Effect of high substrate bias and hydrogen and nitrogen incorporation on density of states and field-emission threshold in tetrahedral amorphous carbon films

Panwar, O. S.; Khan, M. A.; Satyanarayana, B. S.; Bhattacharyya, R.; Mehta, B. R.; Kumar, S.; Ishpal,

doi:doi:10.1116/1.3359586

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Journal of Vacuum Science & Technology B / Volume 28 / Issue 2 / Regular Articles

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J. Vac. Sci. Technol. B 28, 411 (2010); http://dx.doi.org/10.1116/1.3359586 (12 pages)

Effect of high substrate bias and hydrogen and nitrogen incorporation on density of states and field-emission threshold in tetrahedral amorphous carbon films

O. S. Panwar¹, M. A. Khan¹, B. S. Satyanarayana², R. Bhattacharyya³, B. R. Mehta⁴, S. Kumar¹, and Ishpal¹

¹Plasma Processed Materials Group, National Physical Laboratory, Dr. K. S. Krishnan Road, New Delhi 110 012, India
²40, Sreeniketan, NDSE 24, Vasundhara Enclave, New Delhi 110096, India
³National Physical Laboratory, New Delhi 110012, India
⁴Department of Physics, Indian Institute of Technology, Hauz Khas, New Delhi 110016, India

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(Published online 31 March 2010)

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This article reports the influence of substrate bias during growth and of hydrogen and nitrogen incorporation on density of states [N (E_F)] and field-emission threshold (E_turn-on) in tetrahedral amorphous carbon (ta-C) films, deposited using an S-bend filtered cathodic vacuum arc process. The variation in negative substrate bias from −20 to −200 V was found to initially lead to a small decrease in N (E_F) and E_turn-on, and a small increase in the emission current density (J) at 12.5 V/μm in the case of as-grown ta-C films; beyond −200 V substrate bias there is a reversal in the trend. The values of N (E_F) = 1.3×10¹⁷ cm⁻³ eV⁻¹, E_turn-on = 8.3 V/μm, and J = 6.19 mA/cm² were observed at −200 V substrate bias. However at −300 V the properties were not very different from those at −200 V substrate bias and so with a view to use the higher energy, hydrogen and nitrogen incorporation studies were carried out in this condition. It was observed that there was further enhancement in properties with hydrogen and nitrogen incorporation. The best properties measured with in the range of hydrogen and nitrogen incorporation in the present study were N (E_F) = 8.0×10¹⁶ cm⁻³ eV⁻¹, E_turn-on = 7.6 V/μm, and J = 23.7 mA/cm², respectively.

ACKNOWLEDGMENTS

The authors are grateful to the Director, National Physical Laboratory, New Delhi (India), for his kind permission to publish this article. They wish to thank P. N. Dixit, C. M. S. Rauthan, and Abhilasha Chouksey for their help and useful discussion. M.A.K. is grateful to the Ministry of Science and Technology, Government of India, and the Council of Scientific and Industrial Research, Government of India for providing the financial assistance during the course of this work. Ishpal is grateful to the Ministry of Science and Technology, Government of India, for providing the financial assistance.

Article Outline

INTRODUCTION
EXPERIMENTAL DETAILS
RESULTS AND DISCUSSION
1. As-grown ta-C films
  1. SCLC measurements on as-grown ta-C films deposited at different substrate biases
  2. Field-emission measurements of as-grown ta-C films deposited at different negative substrate biases
  3. AFM study of as-grown ta-C films
2. ta-C:H films
  1. SCLC measurements on ta-C:H films deposited at different hydrogen partial pressures
  2. Field-emission measurements of ta-C:H films with different hydrogen partial pressures
  3. AFM study of ta-C:H films
3. ta-C:N films
  1. SCLC measurements on ta-C:N films deposited at different nitrogen contents
  2. Field-emission measurements of ta-C:N films with different nitrogen contents
  3. AFM study of ta-C:N films
4. Comparison of results obtained with those existing in literature and models
CONCLUSION

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KEYWORDS and PACS

Keywords

amorphous state, carbon, current density, electronic density of states, field emission, hydrogen, nitrogen, vacuum deposited coatings, vacuum deposition, density of states, electron field emission, tetrahedral amorphous carbon

PACS

71.23.-k

Electronic structure of disordered solids
79.70.+q

Field emission, ionization, evaporation, and desorption
81.15.-z

Methods of deposition of films and coatings; film growth and epitaxy
68.55.A-

Nucleation and growth
73.21.-b

Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
61.43.-j

Disordered solids

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History

Received 15 July 2009
Accepted 8 February 2010
Published online 31 March 2010

Digital Object Identifier

http://dx.doi.org/10.1116/1.3359586

PUBLICATION DATA

ISSN

1071-1023 (print)

1520-8567 (online)

Publisher

American Vacuum Society

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