Polymorphous Silicon Films Deposited at 27.12 MHz

Abstract

This paper describes, for the first time, a method of producing polymorphous silicon (pm-Si:H) films by plasma-enhanced (PE) CVD, using an excitation frequency of 27.12 MHz. The aim is to produce, at high growth rates, nanostructured films that are more stable than the conventional amorphous or polymorphous silicon films grown by PECVD at 13.56 MHz. The processing data show that, at 27.12 MHz, the pm-Si:H films are produced close to the transition region from amorphous to microcrystalline silicon films, at a growth rate of about 0.3 nm s ±1 , using pressures above 160 Pa. Apart from that, the analysis of the exodiffusion, spectroscopic ellipsometry (SE), and micro Raman data reveal that these films are more dense and compact than the polymorphous films grown at 13.56 MHz.

Nanostructured silicon and its application to solar cells, position sensors and thin film transistors

“…Figure 4 shows typical micro-Raman results of the nanostructured films produced (dotted line) and reference data spectra concerning amorphous (dashed line) and microcrystalline (solid line) silicon thin films. The peak shift observed (from ~480 cm -1 to ~485 cm -1 ) is also seen in polymorphous films and it is attributed to the improvement of the structural order at the nanoscale level [32,54].…”

“…These data, together with the role of hydrogen dilution and P d used, leads to the schematic shown in Figure 6, where a small "window" corresponding to films deposited on the transition region is defined. The transition region where nanostructured films can be processed depends on the reactor configuration and temperature uniformity on the deposition chamber [32,60,61].…”

“…To reach this goal we produced hydrogenated diphasic nanostructured silicon thin films close to the onset of dusty plasma conditions, within the amorphous to microcrystalline transition region, using high hydrogen dilution conditions [32][33][34][35][36].…”

Oxide semiconductors: Order within the disorder

“…On the other hand, the spectra of the a-ZGSO films exhibit a broad band whose peak is shifted to higher energies. This type of behavior is typical of amorphous structures [63][64][65][66][67]. By comparing both films, the poly-ZGO has a higher refractive index in the transparent region than the a-ZGSO.…”

Spectroscopic and Optoelectronic Properties of Hydrogenated Amorphous Silicon-Chalcogen Alloys

“…Hydrogenated polymorphous silicon also proved to be a viable alternative material to produce low-cost solar cells [16]. This material is made up of small clusters containing nanocrystals imbedded in the silicon amorphous matrix.…”