Influence of the postplasma process conditions on the surface conductivity of hydrogenated diamond surfaces

Abstract

It is a common observation that diamond surface conductivity rises after exposure to hydrogen plasmas. Hydrogenation treatments are known to induce a p-type conductive layer, which is not present on non-hydrogenated samples. However, the particular mechanisms predominant in the plasma treatment process are still controversial, and several antagonist conditions have been reported to be of importance, such as sample temperature ͑500°C to 800°C͒, duration ͑a few seconds to 1 h͒, and microwave ͑MW͒ power density, etc. Further, the post-plasma step is also crucial, especially since the surface conductivity has been reported to be affected by the presence of an adsorbate layer on the diamond surface. By setting up the arrangement to enable the in situ measurement of the surface conductivity after treatment, we have been able to control all parameters that could affect the surface conductivity, in order to determine those of importance. Among the parameters studied, we were able to analyze the influence of the surface temperature, the gas phase exposure ͑dry air, wet air, neutral gas, CH 4 , O 2 , and H 2 ), the MW plasma conditions (O 2 ,H 2 ) as well as the exposure to UV ͑Hg and deuterium͒ and the importance of the sequence and duration of each of these treatments. We found that hydrogenated surfaces are strongly influenced by the combination of wet air exposure and UV light. We noticed that the effect of UV light is persistent and cannot be related to direct photoconduction and has to be attributed to a modification of the trapped defect population. This can, therefore, be compared with the modification of filled defect density as observed in persistent photoconduction.

Technology of polycrystalline diamond thin films for microsystems applications

“…Different boron containing compounds typically used for p-type doping are pure boron powder 36 boron trioxide ͑B 2 O 3 ͒, 37 diborane ͑B 2 H 6 ͒, 38,39 and trimethylboron. 44,45 In this work, the boron doping of poly-C film was investigated as a function of TMB/ CH 4 gas ratio, growth temperature and postgrowth an- neal. 40 It has been found that CVD diamond films grown in a hydrogen plasma have a thin hydrogenated surface layer, which becomes conductive after exposure to the atmosphere.…”

Distinctive Glial and Neuronal Interfacing on Nanocrystalline Diamond

“…H-terminated diamonds should be preferred for protein coating, because surface state measurements indicate that the protein coating is thicker on these substrates than on O-terminated diamonds. However, O-terminated diamonds are much more reproducible than H-terminated diamonds, because H-terminated diamonds are less stable and may rapidly become covered with adsorbed species in contact with ambient air, thereby losing their H termination behavior [35] , [36] , [37] , [38] , [39] . This lack of stability may explain the greater variability observed with cultures on H-terminated diamonds.…”

Large deep-ultraviolet photocurrent in metal-semiconductor-metal structures fabricated on as-grown boron-doped diamond

“…It is well known that asgrown CVD diamond films have a high-conductivity ͑p-type conduction͒ layer near the surface, which disappears after oxidation treatment ͑boiling in an acid solution or by exposure to an oxygen plasma͒ and reappears after hydrogen plasma exposure. [9][10][11] Boron-doped diamond thin film was homoepitaxially grown on ͑100͒-oriented 2.5ϫ 2.5ϫ 0.5 mm 3 high-pressure high-temperature Ib Sumitomo substrate using a microwave plasma-enhanced CVD reactor. Boron doping was performed using trimethylboron ͓B͑CH 3 ͒ 3 , TMB͔ as feed gas.…”

“…,10,12 The low dark cura͒ Author to whom correspondence should be addressed; electronic mail: jose.antonio.alvarez@nims.go.jp This article is copyrighted as indicated in the article. Reuse of AIP content is subject to the terms at: http://scitation.aip.org/termsconditions.…”