JVB Nameplate
  • Volume/Page
  • Keyword
  • DOI
  • Citation
  • Advanced
   
 
 
 
Search Issue | RSS Feeds RSS
Previous Issue Next Issue

Jul 2012

Volume 30, Issue 4, Articles (04xxxx)

Issue Cover Spotlight Figure

J. Vac. Sci. Technol. B 30, 041805 (2012); http://dx.doi.org/10.1116/1.4731255 (7 pages)

Meena S. Rajachidambaram, Tamas Varga, Libor Kovarik, Rahul Sanghavi, Vaithiyalingam Shutthanandan, Suntharampillai Thevuthasan, Seung-Yeol Han, Chih-Hung Chang, and Gregory S. Herman
Enlarge Image | Read More
Return to All Sections
back to top
RSS Feeds

Passivation of interfacial defects at III-V oxide interfaces

Liang Lin and John Robertson

J. Vac. Sci. Technol. B 30, 04E101 (2012); http://dx.doi.org/10.1116/1.4710513 (14 pages) | Cited 6 times

Online Publication Date: 2 May 2012

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The electronic structure of gap states has been calculated in order to assign the interface states observed at III-V oxide interfaces. It is found that As-As dimers and Ga and As dangling bonds can give rise to gap states. The difficulty of passivating interface gap states in III-V oxide interfaces is attributed to an auto-compensation process of defect creation which is activated when an electron counting rule is not satisfied. It is pointed out that oxide deposition needs to avoid burying As dimer states from the free surface, and to avoid sub-surface oxidation during growth or annealing, in order to avoid defect states at the interface or in the subsurface semiconductor.
Show PACS
81.65.Rv Passivation
61.72.Cc Kinetics of defect formation and annealing
71.20.Nr Semiconductor compounds
71.55.-i Impurity and defect levels
73.20.At Surface states, band structure, electron density of states

Formation of graphene on SiC(000math) surfaces in disilane and neon environments

Guowei He, Nishtha Srivastava, and Randall M. Feenstra

J. Vac. Sci. Technol. B 30, 04E102 (2012); http://dx.doi.org/10.1116/1.4718365 (6 pages)

Online Publication Date: 15 May 2012

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The formation of graphene on the SiC(000math) surface (the C-face of the {0001} surfaces) has been studied, utilizing both disilane and neon environments. In both cases, the interface between the graphene and the SiC is found to be different than for graphene formation in vacuum. A complex low-energy electron diffraction pattern with √43 × √43-R ± 7.6° symmetry is found to form at the interface. An interface layer consisting essentially of graphene is observed, and it is argued that the manner in which this layer covalently bonds to the underlying SiC produces the √43 × √43-R ± 7.6° structure [i.e., analogous to the 6√3 × 6√3-R30° “buffer layer” that forms on the SiC(0001) surface (the Si-face)]. Oxidation of the surface is found to modify (eliminate) the √43 × √43-R ± 7.6° structure, which is interpreted in the same manner as the known “decoupling” that occurs for the Si-face buffer layer.
Show PACS
81.20.-n Methods of materials synthesis and materials processing
81.65.Mq Oxidation
61.48.Gh Structure of graphene

Optimization of the ammonium sulfide (NH4)2S passivation process on InSb(111)A

Dmitry M. Zhernokletov, Hong Dong, Barry Brennan, Jiyoung Kim, and Robert M. Wallace

J. Vac. Sci. Technol. B 30, 04E103 (2012); http://dx.doi.org/10.1116/1.4719961 (7 pages) | Cited 2 times

Online Publication Date: 22 May 2012

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The passivation of the InSb semiconductor surface and related alloys is of interest due to their small bandgaps and high bulk mobilities, which make them favorable materials for use in quantum-well transistors and long wavelength optoelectronic devices. One of the most common passivation approaches is an ammonium sulfide ((NH4)2S) treatment; however, there are variations in the reported processing conditions for this procedure. This study represents a broad review of the different sulfur treatment parameters used as well as determining the optimal processing parameters in terms of length of time the sample is in the solution and the (NH4)2S concentration, by measuring the level of the residual native oxides, and surface roughness, by means of x-ray photoelectron spectroscopy and atomic force microscopy, respectively.
Show PACS
81.65.Rv Passivation
68.35.B- Structure of clean surfaces (and surface reconstruction)
68.37.Ps Atomic force microscopy (AFM)
68.47.Fg Semiconductor surfaces

Investigation of interfacial oxidation control using sacrificial metallic Al and La passivation layers on InGaAs

Barry Brennan, Marko Milojevic, Roccio Contreras-Guerrero, Hyun-Chul Kim, Maximo Lopez-Lopez, Jiyoung Kim, and Robert M. Wallace

J. Vac. Sci. Technol. B 30, 04E104 (2012); http://dx.doi.org/10.1116/1.4721276 (8 pages) | Cited 1 time

Online Publication Date: 25 May 2012

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The ability of metallic Al and La interlayers to control the oxidation of InGaAs substrates is examined by monochromatic x-ray photoelectron spectroscopy (XPS) and compared to the interfacial chemistry of atomic layer deposition (ALD) of Al2O3 directly on InGaAs surfaces. Al and La layers were deposited by electron-beam and effusion cell evaporators, respectively, on In0.53Ga0.47As samples with and without native oxides present. It was found that both metals are extremely efficient at scavenging oxygen from III–V native oxides, which are removed below XPS detection limits prior to ALD growth. However, metallic Ga/In/As species are simultaneously observed to form at the semiconductor–metal interface. Upon introduction of the samples to the ALD chamber, these metal bonds are seen to oxidize, leading to Ga/In–O bond growth that cannot be controlled by subsequent trimethyl-aluminum (TMA) exposures. Deposition on an oxide-free InGaAs surface results in both La and Al atoms displacing group III atoms near the surface of the semiconductor. The displaced substrate atoms tend to partially oxidize and leave both metallic and III–V oxide species trapped below the interlayers where they cannot be “cleaned-up” by TMA. For both Al and La layers the level of Ga–O bonding detected at the interface appears larger then that seen following ALD directly on a clean surface.
Show PACS
81.65.Rv Passivation
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces
82.80.Pv Electron spectroscopy (X-ray photoelectron (XPS), Auger electron spectroscopy (AES), etc.)
79.60.Bm Clean metal, semiconductor, and insulator surfaces
81.65.Mq Oxidation

Lateral metallic devices made by a multiangle shadow evaporation technique

Marius V. Costache, Germàn Bridoux, Ingmar Neumann, and Sergio O. Valenzuela

J. Vac. Sci. Technol. B 30, 04E105 (2012); http://dx.doi.org/10.1116/1.4722982 (5 pages)

Online Publication Date: 30 May 2012

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The authors report the fabrication of lateral metallic structures with multiple materials using specifically designed resist masks and multiangle shadow evaporation. The whole fabrication process is carried out without breaking vacuum, which avoids contamination and allows for highly controlled interface properties between metals deposited sequentially. The authors incorporate the thickness of the mask as a design parameter, which allows one to introduce controlled variations between multiple contacts in the same device. Using a suspended mask, it is demonstrated the fabrication of asymmetric single electron transistors with tunnel junctions with different resistances. Using a nonsuspended mask, it is illustrated the fabrication of an extended structure (a thermopile), which consists of tenths of ferromagnetic wires with a nominal width of 30 nm connected electrically in series using a nonmagnetic metal.
Show PACS
85.35.Gv Single electron devices

Optical and structural characterization of epitaxial graphene on vicinal 6H-SiC(0001)–Si by spectroscopic ellipsometry, Auger spectroscopy, and STM

Florence Nelson, Andreas Sandin, Daniel B. Dougherty, David E. Aspnes, Jack E. Rowe, and Alain C. Diebold

J. Vac. Sci. Technol. B 30, 04E106 (2012); http://dx.doi.org/10.1116/1.4726199 (6 pages)

Online Publication Date: 8 June 2012

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The authors report results of spectroscopic ellipsometry (SE) measurements in the near-IR, visible, and near-UV spectral ranges using a Woollam dual rotating-compensator ellipsometer, analyzing data in terms of both epitaxial graphene and interface contributions. The SiC samples were cleaned by standard methods of CMP and HF etching prior to mounting in UHV and growing epitaxial graphene by thermal annealing at ∼1400 °C. Most samples were vicinally cut 3.5° off (0001) toward [11−20]. STM measurements show that the initial regular step edges were replaced by somewhat irregular edges after graphene growth. From growth-temperature and Auger data the authors estimate that the graphene is ∼3–4 ML thick. The authors find significant differences among the spectral features of the interface “buffer” layer and those of graphene. Specifically, the hyperbolic-exciton peak reported previously at ∼4.5 eV in graphene shifts to a similarly shaped peak at ∼4 eV in the interface buffer layer. The authors attribute this shift to a significant component of sp3 bonded carbon in the buffer, which occurs in addition to the sp2 bonded carbon that is present in the graphene layer. SE data in the terahertz range obtained by Hoffman et al. [Thin Solid Films 519, 2593 (2011)] show that the mobility values of graphene grown on the carbon face of SiC vary with proximity to the substrate. This leads to the question as to whether an interface layer at the Si face has properties (i.e., dielectric function/complex refractive index) that are different from and/or affect those of the graphene layers.
Show PACS
81.05.ue Graphene
79.20.Fv Electron impact: Auger emission
78.67.Wj Optical properties of graphene
78.40.Ri Fullerenes and related materials
78.30.Na Fullerenes and related materials
61.48.Gh Structure of graphene

Anomalous Rashba effect of bismuth(111) thin films studied by high-resolution spin- and angle-resolved photoemission spectroscopy

Akari Takayama, Takafumi Sato, Seigo Souma, and Takashi Takahashi

J. Vac. Sci. Technol. B 30, 04E107 (2012); http://dx.doi.org/10.1116/1.4731467 (5 pages)

Online Publication Date: 27 June 2012

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The authors have developed an ultrahigh-resolution spin-resolved photoemission spectrometer equipped with a highly efficient mini Mott detector and a high-intensity xenon plasma discharge lamp. An electron deflector situated between the hemispherical electron-energy analyzer and the Mott detector enables the determination of the electron’s spin-polarization in three independent directions and the spectrometer achieves an energy resolution of 0.9 and 8 meV for nonspin-resolved and spin-resolved modes, respectively. By using this spectrometer, we have performed spin- and angle-resolved photoemission spectroscopy of bismuth thin films on Si(111) to investigate the spin structure of surface states. Unlike conventional Rashba splitting, the magnitude of the in-plane spin polarization is asymmetric across the zone center between the two elongated surface hole pockets and there is a giant out-of-plane spin polarization. The authors discuss these unusual spin textures in terms of a possible time-reversal symmetry breaking.
Show PACS
79.60.Bm Clean metal, semiconductor, and insulator surfaces
73.20.At Surface states, band structure, electron density of states
72.25.Ba Spin polarized transport in metals

First-principles study of the growth thermodynamics of Pt on SrTiO3 (001)

Hosung Seo, Agham B. Posadas, and Alexander A. Demkov

J. Vac. Sci. Technol. B 30, 04E108 (2012); http://dx.doi.org/10.1116/1.4732461 (4 pages) | Cited 1 time

Online Publication Date: 29 June 2012

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Using density functional theory, we investigate the growth mode of Pt (001) on SrTiO3 (001) (STO) and explore the thermodynamic wetting conditions at this interface. The authors calculate the surface energy of Pt (001) to be 2.45 J/m2 and that of TiO2-terminated STO (001) to range from 1.30–2.06 J/m2, depending on the chemical environment. The calculated interface energy is 0.37 J/m2 higher than that of the STO (001) surface across the entire thermodynamically allowed range, suggesting that Pt (001) would grow on the STO (001) surface as Volmer–Weber three-dimensional islands. Using Young’s equation, we calculate the contact angle between a Pt (001) island and STO (001) to be between 98.7° and 100.6°.
Show PACS
68.55.aj Insulators
68.35.Ct Interface structure and roughness
68.35.Md Surface thermodynamics, surface energies

Fabrication of an electrical spin transport device utilizing a diazonium salt/hafnium oxide interface layer on epitaxial graphene grown on 6 H-SiC(0001)

Joseph Abel, Akitomo Matsubayashi, Thomas Murray, Christos Dimitrakopoulos, Damon B. Farmer, Ali Afzali, Alfred Grill, C. Y. Sung, and Vincent P. LaBella

J. Vac. Sci. Technol. B 30, 04E109 (2012); http://dx.doi.org/10.1116/1.4732460 (4 pages) | Cited 3 times

Online Publication Date: 2 July 2012

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Nonlocal Hanle spin precession devices are fabricated on wafer scale epitaxial graphene utilizing conventional and scalable processing methods. To improve spin injection and reduce contact related spin relaxation, hafnium oxide is utilized as an interface barrier between the graphene on SiC(0001) and ferromagnetic metal contacts. The hafnium oxide layer is deposited by atomic layer deposition utilizing an organic seed layer. Spin precession is observed in the epitaxial graphene.
Show PACS
72.25.-b Spin polarized transport
75.50.Cc Other ferromagnetic metals and alloys
72.80.Vp Electronic transport in graphene
73.22.Pr Electronic structure of graphene
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping

Schottky barrier and attenuation length for hot hole injection in nonepitaxial Au on p-type GaAs

Ilona Sitnitsky, John J. Garramone, Joseph Abel, Peng Xu, Steven D. Barber, Matt L. Ackerman, J. Kevin Schoelz, Paul M. Thibado, and Vincent P. LaBella

J. Vac. Sci. Technol. B 30, 04E110 (2012); http://dx.doi.org/10.1116/1.4734307 (4 pages)

Online Publication Date: 10 July 2012

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Ballistic electron emission microscopy (BEEM) was performed to obtain current versus bias characteristics of nonepitaxial nanometer-thick Au on p-type GaAs in order to accurately measure the local Schottky barrier height. Hole injection BEEM data were averaged from thousands of spectra for various Au film thicknesses and then used to determine the attenuation length of the energetic charge carriers as a function of tip bias. The authors report an increase in attenuation length at biases near the Schottky barrier, providing evidence for the existence of coherent BEEM currents in Schottky diodes. These results provide additional evidence for the conservation of the parallel momentum of charge carriers at the metal–semiconductor interface.
Show PACS
85.30.Kk Junction diodes
85.30.Hi Surface barrier, boundary, and point contact devices

Growth of epitaxial oxides on silicon using atomic layer deposition: Crystallization and annealing of TiO2 on SrTiO3-buffered Si(001)

Martin D. McDaniel, Agham Posadas, Thong Q. Ngo, Ajit Dhamdhere, David J. Smith, Alexander A. Demkov, and John G. Ekerdt

J. Vac. Sci. Technol. B 30, 04E111 (2012); http://dx.doi.org/10.1116/1.4734311 (6 pages) | Cited 2 times

Online Publication Date: 10 July 2012

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Epitaxial anatase titanium dioxide (TiO2) films have been grown by atomic layer deposition (ALD) on Si(001) substrates using a strontium titanate (STO) buffer layer without any amorphous SiOx layer at the STO–Si interface. Four unit cells of STO grown by molecular beam epitaxy (MBE) serve as the surface template for ALD growth. To preserve the quality of the MBE-grown STO, the samples were transferred in situ from the MBE chamber to the ALD chamber. The growth of TiO2 was achieved using titanium isopropoxide and water as the coreactants at a substrate temperature of 250 °C. In situ x-ray photoelectron spectroscopy analysis revealed that the ALD process did not induce Si–O bonding at the STO–Si interface. Slight improvement in crystallinity of the TiO2 film was achieved through in situ annealing under vacuum (10−9 Torr) at 450–600 °C. However, the amount of Si–O bonding increased following annealing at temperatures greater than 250 °C. X-ray diffraction revealed that TiO2 films annealed at a temperature of 250 °C in vacuum (10−9 Torr) for 1 h were the anatase phase and well crystallized. The results indicate that careful consideration of growth temperature and annealing conditions may allow epitaxial oxide films to be grown by ALD on STO-buffered Si(001) substrates without formation of an amorphous SiOx layer.
Show PACS
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
81.40.Ef Cold working, work hardening; annealing, post-deformation annealing, quenching, tempering recovery, and crystallization
68.55.ag Semiconductors
79.60.Bm Clean metal, semiconductor, and insulator surfaces
Return to All Sections
Close

© 2013 AVS Science & Technology of Materials, Interfaces, and Processing Help | Contact
close