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Sep 2011

Volume 29, Issue 5, Articles (05xxxx)

Issue Cover Spotlight Figure

J. Vac. Sci. Technol. B 29, 050801 (2011); http://dx.doi.org/10.1116/1.3623419 (10 pages)

Robert A. Barton, Jeevak Parpia, and Harold G. Craighead
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Fabrication and performance of graphene nanoelectromechanical systems

Robert A. Barton, Jeevak Parpia, and Harold G. Craighead

J. Vac. Sci. Technol. B 29, 050801 (2011); http://dx.doi.org/10.1116/1.3623419 (10 pages)

Online Publication Date: 9 September 2011

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As a result of the recent progress in fabricating large-area graphene sheets, graphene-based mechanical devices have become vastly easier to manufacture and now show even greater promise for a range of applications. This article reviews the progress of resonant graphene nanoelectromechanical systems and the possible applications of this technology to signal processing, sensing, and other areas. After discussing recent advances in fabrication and measurement techniques that make graphene resonators a viable technology, the article presents what is known about the performance of graphene mechanical systems. The authors also highlight unresolved questions, such as the source of the dissipation in graphene resonators, and discuss the progress made on these issues to date. The authors conclude with a discussion of important future directions for graphene research and the applications for which graphene nanomechanical devices may be well suited.
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81.07.Oj Nanoelectromechanical systems (NEMS)
81.05.ue Graphene
84.40.Az Waveguides, transmission lines, striplines
85.85.+j Micro- and nano-electromechanical systems (MEMS/NEMS) and devices
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Current transport mechanisms of InGaN metal-insulator-semiconductor photodetectors

Z. G. Shao, D. J. Chen, B. Liu, H. Lu, Z. L. Xie, R. Zhang, and Y. D. Zheng

J. Vac. Sci. Technol. B 29, 051201 (2011); http://dx.doi.org/10.1116/1.3622298 (3 pages) | Cited 1 time

Online Publication Date: 11 August 2011

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The authors report on InGaN metal-insulator-semiconductor (MIS) photodetectors with two different insulating layers of Si3N4 and Al2O3 deposited via plasma-enhanced chemical vapor deposition and atomic layer deposition, respectively. The photoresponse spectra show that the metal-Al2O3-InGaN photodetector exhibits an approximately threefold higher photoelectric responsivity and a larger spectral rejection ratio as compared to the metal-Si3N4-InGaN photodetector at a 1 V reverse bias. The current transport mechanisms in MIS photodetectors were investigated in order to determine the difference in photoresponse. The results show that the space charge limited current is a dominant leakage conduction mechanism in the InGaN MIS photodetectors, but this mechanism is mediated by the exponential trap distribution in the metal-Si3N4-InGaN photodetector. This indicates a higher density of trap states in the Si3N4 bulk. A bidirectional Fowler–Nordheim tunneling effect was observed in the metal-Si3N4-InGaN photodetector, which indicates high trap states in the Si3N4 bulk and the Si3N4–InGaN interface. These traps increase the probability of photogenerated carrier recombination in the bulk of the dielectrics and at the interface of dielectric-InGaN, and hence the photoelectric responsivity is lower.
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85.60.Gz Photodetectors (including infrared and CCD detectors)

Etching mechanisms of thin SiO2 exposed to Cl2 plasma

C. Petit-Etienne, M. Darnon, L. Vallier, E. Pargon, G. Cunge, M. Fouchier, P. Bodart, M. Haass, M. Brihoum, O. Joubert, S. Banna, and T. Lill

J. Vac. Sci. Technol. B 29, 051202 (2011); http://dx.doi.org/10.1116/1.3622311 (8 pages)

Online Publication Date: 11 August 2011

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Plasma etching is the most standard patterning technology used in micro- and nano-technologies. Chlorine-based plasmas are often used for silicon etching. However, the behavior of thin silicon oxide exposed to such a plasma is still not fully understood. In this paper, we investigate how a thin silicon oxide layer on silicon behaves when it is exposed to a Cl2 plasma. The authors show that chlorine atoms diffuse and/or Cl+ ions are implanted through the thin (<2.5 nm) oxide, leading to the formation of a SiClx interface layer between the two layers of Si and SiO2. Chlorine accumulates at the interface until the SiO2 is thin enough to release volatile SiClx species and the silicon begins to be etched.
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81.65.Cf Surface cleaning, etching, patterning
81.16.Rf Micro- and nanoscale pattern formation
68.55.aj Insulators

Removing imperceptible fluoride residue after chemical dry-cleaning to fabricate uniform low-resistance NiSi film

Takuya Futase, Hisanori Tanioto, Mitsuo Kimoto, Hideaki Tsugane, Hidenori Suzuki, and Hiroshi Tobimatsu

J. Vac. Sci. Technol. B 29, 051203 (2011); http://dx.doi.org/10.1116/1.3622301 (5 pages)

Online Publication Date: 15 August 2011

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The authors investigated the integrity of the interface between a Ni film and a Si substrate treated by in situ chemical dry-cleaning using ammonium fluorosilicate, or (NH4)2SiF6. In the conventional cleaning scheme, imperceptible fluoride residue at the interface between Ni and Si, even after subliming at 120 °C, was detected by synchrotron x-ray photoelectron spectroscopy. The authors found that the fluoride residue could be removed by additional subliming at 200 °C in a separate chamber following the conventional cleaning scheme (two-step sublimation cleaning). The sheet resistance of nickel monosilicide (NiSi) films fabricated by two-step sublimation cleaning was lower and the NiSi–Si interface was more uniform than for those fabricated by conventional cleaning. This suggests that the fluoride residue triggered the formation of a rough interface between the Ni and Si layers, thus leading to the performance degradation of the NiSi films.
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68.55.-a Thin film structure and morphology
82.80.Pv Electron spectroscopy (X-ray photoelectron (XPS), Auger electron spectroscopy (AES), etc.)
64.70.Hz Solid-vapor transitions
68.35.Ct Interface structure and roughness
79.60.Bm Clean metal, semiconductor, and insulator surfaces

Indium nitride epilayer prepared by UHV-plasma-assisted metalorganic molecule beam epitaxy

Wei-Chun Chen, Shou-Yi Kuo, Fang-I Lai, Woei-Tyng Lin, Chien-Nan Hsiao, and Din Ping Tsai

J. Vac. Sci. Technol. B 29, 051204 (2011); http://dx.doi.org/10.1116/1.3622315 (5 pages)

Online Publication Date: 15 August 2011

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Indium nitride films grown at various growth temperatures were prepared on GaN buffer layers using self-designed plasma-assisted metal-organic molecular beam epitaxy. The influence of substrate temperature on film crystallinity, surface morphology, optical, and electrical properties was studied using x-ray diffraction (XRD), transmission electron microscopy (TEM), field emission scanning electron microscopy (FE-SEM), UV/VIS/NIR spectrophotometer, and Hall measurement. The results show that the InN films grown on the GaN template at 500 oC are of good quality, and the full width at half maximum of InN(0002) ω-scan is around 1000 arc sec. The SEM images revealed that the average growth rate is 1.1 μm/h, which is comparable to the conventional epitaxial techniques. These results indicate that the electronic properties and crystalline quality can be significantly improved by optimizing the growth temperature.
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81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
72.20.My Galvanomagnetic and other magnetotransport effects
68.55.ag Semiconductors
73.61.Ey III-V semiconductors

Influence of sputtering pressure on band gap of Zn1−xMgxO thin films prepared by radio frequency magnetron sputtering

Dapeng Wang, Tadashi Narusawa, Toshiyuki Kawaharamura, Mamoru Furuta, and Chaoyang Li

J. Vac. Sci. Technol. B 29, 051205 (2011); http://dx.doi.org/10.1116/1.3622316 (4 pages)

Online Publication Date: 15 August 2011

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Zn1−xMgxO thin films were deposited onto quartz glass substrates using a radio frequency magnetron sputtering at various deposition pressures. It was found that the Mg concentration in the Zn1−xMgxO thin films significantly increased by decreasing the deposition pressure from 9 to 1 Pa, which contributed to an increase in the band gap of the ZnMgO films. In addition, the Zn1−xMgxO thin films, which had a hexagonal wurtzite structure when obtained by high pressure deposition (7 and 9 Pa) at x ≤ 0.478, had a cubic rock-salt crystal structure when deposition pressure was decreased to 1–5 Pa at x ≥ 0.482. These results show that the band gap of the ZnMgO thin films could be easily modulated only by adjusting of the deposition pressure during the radio frequency sputtering process.
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81.15.Cd Deposition by sputtering
68.55.ag Semiconductors

Large-area and nanoscale n-ZnO/p-Si heterojunction photodetectors

C. Periasamy and P. Chakrabarti

J. Vac. Sci. Technol. B 29, 051206 (2011); http://dx.doi.org/10.1116/1.3628638 (6 pages)

Online Publication Date: 1 September 2011

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The article reports the results of our experimental investigation on the effect of UV light on the characteristics of n-ZnO/p-Si heterojunction. c-Axis oriented zinc oxide (ZnO) films were deposited by thermal evaporation technique on p-type silicon (Si) substrates to form ZnO/Si heterojunctions. Both large-area and nanoscale heterojunction configurations were studied. The measured current–voltage characteristics in dark and illuminated conditions confirm the rectifying behavior of the heterojunctions and an excellent UV response. The responsivity values were measured to be of 0.18 and 0.12 A/W to UV light (365nm) for large-area and nanoscale heterojunctions, respectively. The values are comparable with those offered by other commercial UV detectors. The nanoscale heterojunction device can find applications in nanophotonics.
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85.60.Gz Photodetectors (including infrared and CCD detectors)

X-ray photoelectron spectroscopy measurement of the Schottky barrier at the SiC(N)/Cu interface

Sean W. King, Marc French, Milt Jaehnig, Markus Kuhn, Boyan Boyanov, and Benjamin French

J. Vac. Sci. Technol. B 29, 051207 (2011); http://dx.doi.org/10.1116/1.3633691 (9 pages) | Cited 3 times

Online Publication Date: 16 September 2011

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Electrical leakage in low-k dielectric/Cu interconnects is a continuing reliability concern for advanced <22 nm technologies. One leakage mechanism deserving increased attention is electron transport across the Cu/dielectric capping layer interface. The Schottky barrier formed at this interface is an important parameter for understanding charge transport across this interface. In this report, we have utilized x-ray photoelectron spectroscopy to investigate the Schottky barrier formed at the interface between polished Cu substrates and standard low-k a-SiC(N):H dielectric capping layers deposited by Plasma Enhanced Chemical Vapor Deposition. The authors find the Schottky Barrier at this interface to range from 1.45 to 2.15 eV depending on a-SiC(N):H composition and to be largely independent of various in situ plasma pretreatments.
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73.30.+y Surface double layers, Schottky barriers, and work functions
82.80.Pv Electron spectroscopy (X-ray photoelectron (XPS), Auger electron spectroscopy (AES), etc.)
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Statistical analysis of subnanometer residual disorder in photonic crystal waveguides: Correlation between slow light properties and structural properties

N. Le Thomas, Z. Diao, H. Zhang, and R. Houdré

J. Vac. Sci. Technol. B 29, 051601 (2011); http://dx.doi.org/10.1116/1.3622289 (9 pages)

Online Publication Date: 18 August 2011

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The authors present a statistical study of residual disorder in nominally identical planar photonic crystal waveguides operating in the slow light regime. The focus is on the role played by the subnanometer scaled residual disorder inherent to state-of-the-art electron-beam (EB) lithography systems, in particular, on the impact of the nature of the residual disorder on the maximum value of the guided mode group index. The authors analyze the statistical properties of the surface area, the position, and the shape of the air holes that define the photonic crystal with optimized scanning electron microscope micrographs. The authors identify the hole-area fluctuation as the main source of degradation of the dispersive slow light regime by correlating such a microscopic analysis of the structural disorder with large field-of-view optical characterizations based on a Fourier space imaging technique. The structure with the largest group index (ng = 40) exhibits a standard deviation σ of the radius of the hole as low as 0.4 nm. Such a low value of σ, which already significantly limits the maximum achievable group index of the guided mode, stresses the drastic impact of the residual disorder on the performances of the slow light regime. A mean square analysis of the electronic micrographs reveals that the standard deviation of the hole position is lower than an upper limit of 0.6 nm. This upper bound comes from the intrinsic imperfections of the scanning electronic microscope itself, which hinders to quantify the position disorder induced by the EB lithography system. The authors have identified no correlation between the shape of the holes and the group index as for the hole position. As a result, the hole-area fluctuation is currently the main parameter to control in order to improve the performance of the slow light regime.
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42.70.Qs Photonic bandgap materials
02.50.-r Probability theory, stochastic processes, and statistics
05.40.-a Fluctuation phenomena, random processes, noise, and Brownian motion

Novel fabrication technique for nanoscale hydrogen silsesquioxane structures using a direct printing technique

Ki-Yeon Yang, Sang-Chul Oh, Hyungwon Park, and Heon Lee

J. Vac. Sci. Technol. B 29, 051602 (2011); http://dx.doi.org/10.1116/1.3628585 (4 pages)

Online Publication Date: 29 August 2011

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Hydrogen silsesquioxane (HSQ), a type of spin-on glass, is an attractive material for nanobio, semiconductor and photoelectronic applications because it can be transformed into SiO2 by a simple annealing process. Studies on the fabrication of nanosized structures are necessary for the simple and easy production of HSQ nanostructures because of their unique characteristics. In this study, a fabrication method was developed for HSQ nanostructures as small as 50 nm using a direct printing technique with a poly (dimethylsiloxane) (PDMS) mold. Using this technique, HSQ nanostructures can be fabricated on a curved substrate
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81.16.Rf Micro- and nanoscale pattern formation
81.07.Bc Nanocrystalline materials
61.46.-w Structure of nanoscale materials

Large area microcorrals and cavity formation on cantilevers using a focused ion beam

Laxmikant V. Saraf and David W. Britt

J. Vac. Sci. Technol. B 29, 051603 (2011); http://dx.doi.org/10.1116/1.3626833 (5 pages)

Online Publication Date: 14 September 2011

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The authors utilize a focused ion beam (FIB) to explore various sputtering parameters in order to form large area microcorrals and cavities on cantilevers. Microcorrals were rapidly created by modifying ion beam blur and overlaps. Modifications of the FIB sputtering parameters affect the periodicity and shape of the corral microstructure. Cantilever deflections show ion beam amorphization effects as a function of the sputtered area and cantilever base cavities with or without side walls. The FIB sputtering parameters address a method for the rapid creation of a cantilever tensiometer with integrated fluid storage and delivery.
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81.15.Jj Ion and electron beam-assisted deposition; ion plating
85.40.Sz Deposition technology
47.85.Np Fluidics
85.85.+j Micro- and nano-electromechanical systems (MEMS/NEMS) and devices
81.15.Cd Deposition by sputtering

Low energy micron size beam from inductively coupled plasma ion source

P. Y. Nabhiraj, Ranjini Menon, R. K. Bhandari, G. Mohan Rao, and S. Mohan

J. Vac. Sci. Technol. B 29, 051604 (2011); http://dx.doi.org/10.1116/1.3640851 (6 pages)

Online Publication Date: 22 September 2011

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A high brightness inductively coupled plasma ion source based focused ion beam system is being developed. This system is intended to produce a low energy high current micron size beam of the heavier gaseous elements for high speed, micro milling applications. The basic aim of this development is to cater the needs of those applications which cannot be addressed by the conventional liquid metal ion source based FIB. A novel idea has been implemented in the design of the ion source where, a double plasma chamber is designed to initiate the plasma at low RF power. The plasma is first initiated by the capacitive coupling at low RF power in one chamber. This in turn triggers a strong, high density inductive discharge in another chamber, which is Faraday shielded by a thin slotted copper foil. The ion beam is extracted through 1 mm diameter aperture in the plasma electrode using a simple two electrode extraction system. The ion source has produced argon ion beam of 57 mA/cm2 with an angular current density of ∼10 mA/Sr at 160 W of RF power and 7kV of extraction voltage. In addition, the measurements show that the ion source has brightness of >8000 A/m2 Sr−1 V−1. The ion source is integrated with a two lens focusing column and beam currents from 2 nA to 2.5 μA were focused at a working distance of 5 mm. Measurements show that the currents in the range of 500 nA to 1 μA can be focused to spots having diameters in the range of 8–10 μm resulting in a current density of 450 mA/cm2 at the focused spot. In order to evaluate the milling rate of steel, experiments were carried out using 7 keV, 800 nA of argon ion beam. Preliminary results indicate that the milling rate of steel is >100 μm3/s.
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52.50.Dg Plasma sources
52.59.-f Intense particle beams and radiation sources
07.77.Ka Charged-particle beam sources and detectors
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Optimization of postgrowth electron-beam curing for focused electron-beam-induced Pt deposits

Harald Plank, Gerald Kothleitner, Ferdinand Hofer, Stephan G. Michelitsch, Christian Gspan, Andreas Hohenau, and Joachim Krenn

J. Vac. Sci. Technol. B 29, 051801 (2011); http://dx.doi.org/10.1116/1.3622314 (7 pages)

Online Publication Date: 15 August 2011

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The authors use focused electron-beam-induced Pt deposition from a gaseous (CH3)3CH3C5H4Pt precursor for the fabrication of electrically conductive structures consisting of Pt nanocrystals embedded in a carbon containing matrix. Recently it has been demonstrated that the electrical resistivity of such deposits can be strongly improved via postgrowth electron irradiation. This study shows very strong evidence that incompletely and nondissociated precursor molecules incorporated within the deposits during deposition are the key elements for efficient e-beam curing. During the early stages of e-beam curing these fragments are further dissociated, which leads to slight growth of the Pt nanocrystals. This is further supported by variable growth regime experiments during deposition which can be used to enhance the incorporation of incompletely and nondissociated precursor molecules, resulting in higher curing efficiencies and lower electrical resistivities. The absence of a predominant graphitization of the surrounding carbon matrix during this dissociation dominated curing regime suggests strongly that the observed resistivity decrease is mainly caused by the formation of preferred tunnel percolation paths due to reduced intercrystallite distances. Furthermore, it is shown that deposit height and the electron-beam energy used for curing should be adapted to each other to achieve the fastest curing time and the lowest electrical resistivities. Such optimized procedures allow then for curing rates higher than 1.5 μm2 min−1 and resistivity decreased to 5 ± 0.4 × 104 μΩ cm, representing an improvement of up to 3 orders of magnitude.
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81.07.Bc Nanocrystalline materials
73.61.At Metal and metallic alloys
61.80.Fe Electron and positron radiation effects
81.15.Jj Ion and electron beam-assisted deposition; ion plating

Silicon nitride nanotemplate fabrication using inductively coupled plasma etching process

Asma Ayari-Kanoun, Abdelatif Jaouad, Abdelkader Souifi, Dominique Drouin, and Jacques Beauvais

J. Vac. Sci. Technol. B 29, 051802 (2011); http://dx.doi.org/10.1116/1.3628593 (5 pages)

Online Publication Date: 29 August 2011

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In this work, we have investigated the fabrication of ordered silicon nitride nanohole arrays as part of an overall process aimed at producing organized silicon nanocrystals. The authors have demonstrated that it is possible to use inductively coupled plasma etching systems in order to etch nanometric layers, despite the fact that these systems are designed for deep and fast etching. A stable process is developed for shallow etching of silicon nitride nanoholes. The influence of different plasma etching parameters on silicon nitride nanohole properties is analyzed. 30 nm deep nanoholes of approximately 30 nm diameter, near vertical sidewalls and a good control of the selectivity are achieved. The overall process provides a simple and reproducible approach based on shallow inductively coupled plasma etching to obtain high quality nanosized silicon nitride templates. A suitable process for organized arrays of 10 nm diameter silicon nanocrystals realized by electrochemical etching is shown.
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81.16.-c Methods of micro- and nanofabrication and processing
52.77.Bn Etching and cleaning
81.65.Cf Surface cleaning, etching, patterning
81.07.Bc Nanocrystalline materials
81.05.Cy Elemental semiconductors
82.45.-h Electrochemistry and electrophoresis

Characterization of Mo/Si multilayer growth on stepped topographies

A. J. R. van den Boogaard, E. Louis, E. Zoethout, K. A. Goldberg, and F. Bijkerk

J. Vac. Sci. Technol. B 29, 051803 (2011); http://dx.doi.org/10.1116/1.3628640 (6 pages)

Online Publication Date: 1 September 2011

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Mo/Si multilayer mirrors with nanoscale bilayer thicknesses have been deposited on stepped substrate topographies, using various deposition angles. The multilayer morphology at the step-edge region was studied by cross section transmission electron microscopy. A transition from a continuous- to columnar layer morphology is observed near the step-edge, as a function of the local angle of incidence of the deposition flux. Taking into account the corresponding kinetics and anisotropy in layer growth, a continuum model has been developed to give a detailed description of the height profiles of the individual continuous layers. Complementary optical characterization of the multilayer system using a microscope operating in the extreme ultraviolet wavelength range, revealed that the influence of the step-edge on the planar multilayer structure is restricted to a region within 300 nm from the step-edge.
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68.65.Ac Multilayers
78.66.Db Elemental semiconductors and insulators
81.16.-c Methods of micro- and nanofabrication and processing
68.35.B- Structure of clean surfaces (and surface reconstruction)
68.55.-a Thin film structure and morphology
61.46.-w Structure of nanoscale materials

Mueller polarimetry as a tool for detecting asymmetry in diffraction grating profiles

Tatiana Novikova, Pavel Bulkin, Vladimir Popov, Bicher Haj Ibrahim, and Antonello De Martino

J. Vac. Sci. Technol. B 29, 051804 (2011); http://dx.doi.org/10.1116/1.3633693 (6 pages)

Online Publication Date: 9 September 2011

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Reflected Mueller matrix spectra were measured and simulated for asymmetrical photoresist master diffraction gratings in conical mounting (i.e., the direction of grating grooves was not perpendicular to the plane of light incidence). From the electromagnetic reciprocity theorem, Mueller matrix of symmetric grating (composed of only reciprocal materials, and operating in zeroth-order diffraction) is invariant under transposition ( M = Mt). For zeroth-order diffraction of asymmetric gratings, the lack of profile rotational symmetry violates this reciprocity and, consequently, breaks the symmetry of the above-mentioned matrix. This property of the Mueller matrix of asymmetric gratings was experimentally observed and numerically modeled at all experimental illumination conditions with the exception of planar mounting (the direction of grating grooves was perpendicular to the plane of light incidence), where there is no cross-polarization effect for the gratings composed of isotropic materials. It was demonstrated that optical nonreciprocity of diffraction gratings can be used for unambiguous detection of grating profile asymmetry. In addition, choosing optimal measurement configuration (i.e., azimuthal angles) considerably increases the sensitivity of the detection technique.
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42.79.Dj Gratings
42.25.Gy Edge and boundary effects; reflection and refraction
07.60.Fs Polarimeters and ellipsometers

Effect of nanoscale ripples on the formation of ZnO quantum dots

Liang-Chiun Chao, Wei-Ruei Chen, Jun-Wei Chen, Syuan-Miao Lai, and Gerd Keiser

J. Vac. Sci. Technol. B 29, 051805 (2011); http://dx.doi.org/10.1116/1.3633689 (4 pages)

Online Publication Date: 12 September 2011

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Nano-scale ripples on Si (100) substrates were prepared by argon ion beam sputtering at 6, 8, and 10 keV with an ion fluence of 5 × 1017 ions/cm2. The spatial wavelength of the nano-scale ripple increases as the ion beam energy increases, regardless of ion beam incident angles, indicating that ion beam induced diffusion is the dominant diffusion mechanism. ZnO quantum dots (QDs) with diameters less than 20 nm and heights less than 4 nm can be prepared over the temperature range from 200 ∼ 300 °C by reactive ion beam sputter deposition. Compared with ZnO QDs deposited on Si substrates without nano-scale ripple, the ion-beam textured substrate provides a wider processing window, improved dot size, and increased QD density.
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81.07.Ta Quantum dots
81.05.Dz II-VI semiconductors
81.15.Cd Deposition by sputtering
81.16.-c Methods of micro- and nanofabrication and processing
61.80.Jh Ion radiation effects
66.30.Pa Diffusion in nanoscale solids

Releasable infrared metamaterials

J. A. D’Archangel, G. D. Boreman, D.J. Shelton, M. B. Sinclair, and I. Brener

J. Vac. Sci. Technol. B 29, 051806 (2011); http://dx.doi.org/10.1116/1.3633695 (5 pages)

Online Publication Date: 14 September 2011

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Infrared metamaterial arrays containing Au elements immersed in a medium of benzocyclobutene (BCB) were fabricated and selectively etched to produce small square flakes with edge dimensions of approximately 20 μm. Two unit-cell designs were fabricated successfully: one employed crossed-dipole elements while the other utilized square-loop elements (the latter design was symmetric about a Cr ground plane). Infrared spectral reflectivity measurements from collected flakes were compared to infinite-surface simulations in Ansoft HFSS and spectral reflectance measurements of full array samples. Good agreement was found between modeled and experimental resonant behavior when taking into account the proportionality of flakes filling the input aperture of the measurement apparatus.
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78.67.Pt Multilayers; superlattices; photonic structures; metamaterials
81.05.Xj Metamaterials for chiral, bianisotropic and other complex media
42.70.-a Optical materials
78.20.-e Optical properties of bulk materials and thin films
78.30.Er Solid metals and alloys
42.82.Cr Fabrication techniques; lithography, pattern transfer

In-process characterization tool for optically produced sub-100-nm structures

M. Z. Shaikh, S. Kieß, M. Grégoire, S. Simon, A. Tausendfreund, M. Zimmermann, and G. Goch

J. Vac. Sci. Technol. B 29, 051807 (2011); http://dx.doi.org/10.1116/1.3635404 (5 pages)

Online Publication Date: 20 September 2011

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In this paper an in-process measurement tool based on coherent laser light scattering by sub-100-nm structures is presented. Laser beams of high fluence are used for fabricating three-dimensional nanostructures in the sub-100-nm range for different applications and measurement of these nanostructures is vital during manufacturing for quality control, defect analysis, calibration measurements, etc. However, present offline measurement techniques such as atomic force microscopy and scanning electron microscopy prove to be too slow and, in some cases, also destructive. It is shown that by measuring the scattered laser light distribution of nanostructures such as zinc-oxide nanograss, it is possible to distinguish between defect-free and defective nanostructures. This allows for fast, contactless and nondestructive measurements of nanostructures. Using discrete dipole approximation (DDA) to simulate the scattered laser light distribution of modeled zinc-oxide nanograss and also CCD optical measurements of commercial grade nanograss, a correlation between the two sets of measurements strongly supports the concept of a tool capable of providing measurements of sub-100-nm nanostructures in a running manufacturing process.
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81.70.Fy Nondestructive testing: optical methods

Improved estimation of embedded InGaAs/GaAs quantum dots locations using a domed-apex nanoprobe

Lixia Xu, Yoshio Arai, Wakako Araki, Takahiro Ogawa, Kazunari Ozasa, Mizuo Maeda, and Masahiko Hara

J. Vac. Sci. Technol. B 29, 051808 (2011); http://dx.doi.org/10.1116/1.3628632 (4 pages)

Online Publication Date: 27 September 2011

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An improved ability to estimate locations of embedded InGaAs/GaAs quantum dots (QDs) was demonstrated by using a domed-apex probe to measure low-temperature (10 K) photoluminescence (PL) during a nanoprobe scan. Individual QDs subjected to nanoprobe-induced strain exhibited enhanced fine PL peaks. PL emission results were used to trace locations of single QDs to the probe positions where their PL peak energies achieved maximum values.
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78.67.Hc Quantum dots
78.55.Cr III-V semiconductors
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Gallium nitride nanowire electromechanical resonators with piezoresistive readout

Jason M. Gray, Charles T. Rogers, Kris A. Bertness, and Norman A. Sanford

J. Vac. Sci. Technol. B 29, 052001 (2011); http://dx.doi.org/10.1116/1.3622326 (4 pages)

Online Publication Date: 11 August 2011

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The authors report on the fabrication, piezoresistive readout, and frequency response of doubly clamped c-axis gallium nitride nanowire (NW) resonators that show mechanical quality factors exceeding 10 000. The devices are fabricated using a combination of lithographic patterning and dielectrophoresis to suspend NWs across 10 μm gaps. An electrostatic gate induces NW vibration, which is electronically detected via NW piezoresistance. The naturally occurring range of NW diameters results in lowest beam resonances in the range of 9–36 MHz, consistent with a Young’s modulus of roughly 300 GPa. Mechanical quality factors, Q, as high as 26 000 under vacuum at 8 K are observed. Selective variation of NW temperature by local joule heating while maintaining cold mechanical clamps demonstrates the dominant role of the polycrystalline metallic end clamps in the room-temperature mechanical dissipation.
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84.32.Ff Conductors, resistors (including thermistors, varistors, and photoresistors)
85.30.De Semiconductor-device characterization, design, and modeling
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Electronic properties of ultrathin high-κ dielectrics studied by ballistic electron emission microscopy

H. L. Qin, C. Troadec, K. E. J. Goh, K. Kakushima, H. Iwai, M. Bosman, and K. L. Pey

J. Vac. Sci. Technol. B 29, 052201 (2011); http://dx.doi.org/10.1116/1.3622296 (5 pages) | Cited 1 time

Online Publication Date: 15 August 2011

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Ballistic electron emission microscopy was employed in order to investigate the electronic properties of sub-nanometer high-κ dielectrics (CeO2 and La2O3). The authors found that such a thin dielectric sandwiched between Au and n-Si fails to exhibit the same electronic barrier as its bulk counterpart, but it can still significantly attenuate the ballistic electron transport. The authors attribute the observed smaller barrier height to quantum tunneling and/or induced gap states. The results suggest that such ultrathin high-κ dielectrics in a metal-dielectric-semiconductor structure do not show a fully formed electronic barrier.
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73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
73.40.Gk Tunneling
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Organic thin-film transistors with electron-beam cured and flash vacuum deposited polymeric gate dielectric

Gamal Abbas, Hazel Assender, Mervat Ibrahim, and D. Martin Taylor

J. Vac. Sci. Technol. B 29, 052401 (2011); http://dx.doi.org/10.1116/1.3628635 (4 pages)

Online Publication Date: 2 September 2011

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The electrical characteristics of pentacene organic field effect transistors (OFETs) based on cross-linked acrylic insulator as the gate dielectric are reported. Vacuum deposited thin films of cross-linked tripropyleneglycol diacrylate could be obtained by ultrahigh flash evaporation rate and subsequent irradiation using an electron-beam source. The characteristics of common gate OFETs, on highly conductive Si substrate, were tuned through the ease of control of the acrylic dielectric thickness achieving, without surface modification of the dielectric layer, a field effect mobility value of 0.09 cm2 V−1 s−1, a threshold voltage of 10 V, and an on/off current ratio of 1.3 × 103. This work could provide an alternative route to low cost and large area organic electronics manufacturing.
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85.30.Tv Field effect devices
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Embedding a carbon nanotube across the diameter of a solid state nanopore

E. S. Sadki, S. Garaj, D. Vlassarev, J. A. Golovchenko, and D. Branton

J. Vac. Sci. Technol. B 29, 053001 (2011); http://dx.doi.org/10.1116/1.3628602 (4 pages)

Online Publication Date: 1 September 2011

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A fabrication method for positioning and embedding a single-walled carbon nanotube (SWNT) across the diameter of a solid state nanopore is presented. Chemical vapor deposition (CVD) is used to grow SWNTs over arrays of focused ion beam (FIB) milled pores in a thin silicon nitride membrane. This typically yields at least one pore whose diameter is centrally crossed by a SWNT. The final diameter of the FIB pore is adjusted to create a nanopore of any desired diameter by atomic layer deposition, simultaneously embedding and insulating the SWNT everywhere but in the region that crosses the diameter of the final nanopore, where it remains pristine and bare. This nanotube-articulated nanopore is an important step towards the realization of a new type of detector for biomolecule sensing and electronic characterization, including DNA sequencing.
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81.16.-c Methods of micro- and nanofabrication and processing
61.46.Fg Nanotubes
61.48.De Structure of carbon nanotubes, boron nanotubes, and other related systems
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
87.16.-b Subcellular structure and processes
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
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