Studies of the Growth and Doping of Diamond Thin Films

Abstract

Ema I I 1 I 1 A r h J v o rs c 2. k @ c h. doe. g ob Office of triit?iiec:ual Property Law 3 0 E Chicago Operatrons Office The objective of this research is to fabricate diamond thin films suitable for device fabrication, and to dope these filnis in order to obtain n-type semiconducting behavior. Chemical vapor deposition (CVD) is used to grow the films, and ZM .situ ellipsometry is used to monitor the growing surface. Sulfur doping is accomplished by the addition of trace amounts of IH2S. Hall conductivity measurements show that the sulfur-incorporated films are n-type with conductivities around 100 S/cm. The surface roughness and growth rate were simultaneously improved by a factor of ten as a result of sulfur addition. The as-gi-o\vn tilms look transparent and shiny. The surface roughness of these films is 20-50 nm, as nieasured by A F M , \vhich is one order of magnitude lower than typical CVD microcrystalline diamond. Since the presence of sulfur changes the overall surface and gas reaction kinetics. systematic gro\vtli studies as ;L liinction of su I fu r concentration, ni et h an e co 11 cent ration. s ti bs t ra te te in p e ratu re. and gas p rcs su I ' C ;I I'C needed and underway. The results obtained enable the Fabrication 01' small device structures (I ~i m interdigit spacing) on diamond tilms and make diamond a more viable material for' commercial applications. Moreover, the hot filament chemical vapor deposition system employed is much easier to upscale than other types of enhanced CVDs, and it has the additional advantage of being relatively insensitive to the presence of molecular nitrogen, which is the iiia.ioi-source of unintentional doping in microwave CVDs. In the second phase of this research prqject. prototype electronic device structures will be fabricated on semiconducting diamond tilms in order to evaluate their UV sensing and electron field emitting characteristics. Suinniaiy of Accomplishments: Sulfur-incorporated tilins are n-type with conductivities around 100 Sicin. Growth rates were increased by a factor often to around I 5 pm/hr. Surface roughness was lowered in one order ol'magnitude to wound 20-50 n m. The as-grown tilnis are transparent and shiny, requiring no polishing. S in oo t h se in icon du ct i ng diamond ti I ins enab I e the fab r i cat i on d i ani o n d e I ect 1'0 n i c (1 c v i cc's