Raman study of thin films of amorphous-to-microcrystalline silicon prepared by hot-wire chemical vapor deposition

Abstract

The structure changes of thin films of amorphous ͑a͒ to microcrystalline (c) silicon are studied by Raman scattering in terms of three deposition parameters: the silane flow rate, the hydrogen flow rate, and the total gas pressure in hot-wire chemical vapor deposition. The Raman transverse optical ͑TO͒ mode is deconvoluted into two Gaussian functions for a-Si:H and intermediate components and one Lorenzian function for the c-Si component. We found that ͑a͒ in general, the change in structure is a function of the ratio of hydrogen to silane gas flow, R, but also depends on the SiH 4 flow rate and total gas pressure; ͑b͒ there is a narrow structural transition region in which the short-range order of the a-Si:H network improves, i.e., the variation in bond angle of the a-Si network decreases from ϳ10°to ϳ8°once the c-Si grains start to grow; and ͑c͒ when the films were deposited using a high SiH 4 flow rate of 22 sccm, the narrow TO mode with low peak frequency could be related to the column-like structures.

Optoelectronic properties of hot-wire silicon layers deposited at 100°C

“…Another cause of this delayed transition can lie in the fact that the dilution was changed by varying the hydrogen flow and keeping the silane flow constant for the 100 microbar series and oppositely for the 50 microbar series. A similar observation concerning the increase of the crystallinity threshold with the increase in the silane flow was made in an extensive study of HWCVD films deposited at 240°C around the amorphous-to-microcrystalline transition [7]. The photoresponse is more or less constant within the 100 microbar series, with values smaller than 10 4 , while the E u shows an improvement from values higher than 90 meV to values less than 80 meV with increasing dilution.…”

High‐Throughput Chemical Vapor Deposition System and Thin‐Film Silicon Library

“…The c-Si volume faction can be calculated from fitting the spectra with three components: a-Si:H, grain boundary, and c-Si. [17][18][19] At low R (<3), most films are in an amorphous phase, except for the low flow rate of 3 sccm. X c increasing with increasing R suggests that R is a good indicator that correlates well to the structure change from a-Si:H to mc-Si, as used by many research groups.…”

Control of Surface Chemistry and Electrochemical Performance of Carbon-coated Silicon Anode Using Silane-based Self-Assembly for Rechargeable Lithium Batteries

“…Raman spectrum of the film in Fig. 1b exhibits a sharp band at 516 cm -1 , characteristic of crystalline Si, 27 and equally intense and broad bands at 141, 320 and 472 cm -1 that are due to amorphous Si. 28,29 Although the as-prepared Si only film was crystalline, discernable from the XRD pattern (not shown), after carbon-coating the film became partly disordered or amorphous.…”