Real Time Monitoring of the Crystallization of Hydrogenated Amorphous Silicon

Abstract

In-situ real-time optical reflectance spectroscopy is applied to investigate structural changes as hydrogenated amorphous silicon (a-Si:H) loses H and crystallizes at elevated temperature. The interference fringe spectrum (cutoff energy and amplitude) mainly characterize changes in the bulk, while the the crystal Si (c-Si) direct-transition ultra-violet reflectance signatures reveal the presence of any crystalline phase at the surface. Effusion of atomic hydrogen is monitored by a decrease of the interference fringe cutoff energy and is thermally activated with about 1.7 eV. In a-Si:H on glass, optical reflectance spectra are consistent with 2.8 eV activated homogeneous nucleation and growth of a small grain (~100 nm) polycrystalline phase. In contrast, a-Si:H on c-Si crystallizes by solid phase epitaxy with very different spectral kinetics. Our measurements reveal the temperature-time window for thermal crystallization of a-Si:H for photovoltaic device applications, and highlight the versatility of the in-situ spectral reflectance monitoring.

Ultra-high material-quality silicon pillars on glass

“…The results indicated that most silicon pillars usually contain only 1-3 grains, which indicates that large grains can easily be achieved under such high-frequency, short-time millimeter wave annealing conditions. No preferential grain orientation was observed, which is similar to the case in SPC or cw laser crystallization of a-Si, as well [13,14]. In addition, our results indicate that pillar growth occurred normal to the substrate.…”

A new approach to thin film crystal silicon on glass: Biaxially-textured silicon on foreign template layers

“…A key advantage of solid-phase epitaxy is that it is a simple and scalable process. On Si substrates, the amorphous silicon precursor layer can be deposited very rapidly (up to 10 nm/s) [19] and films can be crystallized using batch annealing. However, we are unaware of any research on Si SPE on foreign materials.…”

“…Using SPE, several microns of epitaxial film have been grown on (1 0 0) silicon wafers during a single step [19]. Thus, SPE could be an effective film thickening technique if repeated amorphous silicon growth and annealing steps are employed.…”

Combinatorial Studies of Switching and Solid-Phase Crystallization in Amorphous Silicon

“…It has been successfully employed in thin-film Si research [3]. In this work, we demonstrate the effectiveness of this approach in two areas of our research: 1) creation of an inexpensive, writeonce thin film Si electrical digital memory [4][5][6] and 2) study of the kinetics of the solid-phase epitaxy of Si for photovoltaic applications [7].…”

“…6 V, to a selected element it switches to a permanent low-resistance state (logical 1) and can be detected by the high forward current of through the underlying diode. However, it is important to know the maximum SPE layer thickness, which is limited by a competition between the SPE from the crystalline substrate interface and the random crystallization in the bulk of a-Si:H film [7]. For the thin-film Si diode, high forward current is necessary for the switching of the switch layer as well as for the detection of the ON-state once it has been formed.…”