Optical properties of μc-Si:H/α-Si:H layered structures: Influence of the hydrogen bonds, crystallite size, and thickness

Abstract

Thin films of layered μc-Si:H/α-Si:H structures grown with rf magnetron sputtering have been studied with spectroscopic ellipsometry (SE) and Raman spectroscopy (RS). Analysis of the dielectric function spectra with the Si-centered tetrahedron model and deconvolution of the Raman spectra suggest that the silicon-hydrogen bonds are correlated with the microscopic voids in α-Si:H while the good quality α-Si:H films exhibit SiH3 bonds and small amount of SiH2 bonds. The quality of the surface and interface of the μc-Si:H/α-Si:H was analyzed by SE and transmission electron microscopy and the dependence of an interfacial amorphous layer at the initial stages of the μc-Si:H growth on the argon and hydrogen pressure was found. Furthermore, a correlation between the SE and RS results on μc-Si:H layers is shown and commented, while a dependence of the energy shift and the broadening of the interband transitions and the Raman transverse optical peak on the mean crystallite size has been found and discussed in view of the finite size and stress effects on the electronic structure of these materials. This analysis suggests that strain is one of the most important factors during the growth of μc-Si:H.

Optical studies of phosphorus-doped poly-Si films

“…Calculating the energy of the singlet is quite involved (10-13), but the final result is the following: Under a (001) biaxial stress, the change in the Raman shift of the singlet is Ao3=(p~J2o~o)+qexx/mo=b~, where p and q were determined in (11) resulting in b=-831 cm -t. The stress is thus X=-Aox0.217 GPa/cm l, since X=exl80 GPa. Since our grain sizes and film thicknesses are large, the position of the Raman peak is not affected by confinement (14)(15).…”

“…4 (symbols). Next, we fit the derivative in the E1 region with the simple 2-D analytical lineshape (14)(15)(16) -2500 3.1 3.2 3.3 3.4 3.5 3.6 Energy (eV) FIGURE 4. Second derivative of the dielectric function for wafer #24 in the Ej critical-point range (symbols) along with a fit to the data using analytical lineshapes (lines).…”

Effects of prior hydrogenation on the structure and properties of thermally nanocrystallized silicon layers

“…Such a partial crystallization is in accordance with previous reports dealing with similar predominance of hydrogen partial pressure in the sputtering plasma. 24,25 The desorption of hydrogen accompanying the direct crystallization has been already noticed 6,26,27 and is generally ascribed to complex interactions between the silicon hydrides ͑Si-H 2 , Si-H 3 ͒ produced by the reactive sputtering of the silicon target by hydrogen, on the one side, and the weak or strained bonds at the growing surfaces, on the other side. This is known to lead to the crystalline state, together with the formation of volatile species such as SiH 4 , Si 2 H 6 , and H 2 .…”

Characterizations of nanostructured silicon‐carbon films deposited on p‐layer by PECVD

“…On the other hand, the initial roughness [20,22] associated with very thin p-layer on SnO 2 substrate facilitates the mobility of the reaction precursors, thus enhancing the nucleation process and accordingly the crystalline phase growth for the films deposited on p/SnO 2 as compared to the films deposited on Corning glass. Clearly the morphology of the different substrates, under suitable the deposition conditions, determines the nucleation process and therefore the crystalline fraction and the size of the crystallites.…”