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A. M. Ali, T. Inokuma, Y. Kurata and S. Hasegawa Department of Electronics, Faculty of Technology, Kanazawa University, Kanazawa 920-8667, Japan

ABSTACT Nanocrystalline silicon (nc-Si) films were deposited on fused quartz and single (100) crystal Si substrates by plasma-enhanced chemical vapor deposition from a SiH 4-H2 mixture at various deposition temperaturesTd. The effects of plasma-assisted hydrogenation at 300 TC on the optical and structural properties were examined for the nc-Si films. The film deposited at Td = 730 'C exhibits photoluminescence (PL) in its as-deposited state, but the intensity of PL decreases after hydrogenation. We find that a correlation between the PL intensity and infrared absorption bands at around 850 and 1000 cm-1. INTRODUCTION Nanocrystalline silicon (nc-Si) and polycrysilline silicon (poly-Si) are expected to be applied to optoelectronic devices, optical interconnections, electroluminescence devices, and thin film transistors (TFTs). Because such materials would be suitable with the existing industrial infrastructure for ultra-large scale integrated circuits, and its higher mobility than that of amorphous Si (a-Si). In addition, the intensive photoluminescence (PL) at room temperature has attracted much attention for nc-Si films. However, the mechanism of the observed visible PL is still unclear; Some researchers attribute the PL to quantum size effects in the Si nanostructures [1-4] while others attribute it to a-Si [5,6], siloxene [7,8], hydrides/polysilanes [9,10] and

oxygen-related defect centers [11-13]. Plasma-enhanced chemical vapor deposition (PECVD) is one of methods to grow nc-Si and poly-Si films having some advantages such as low deposition temperature and large-area deposition. The PECVD nc-Si thin films usually contain randomly orientated nanocrystals (5-50 nm) embedded in a hydrogenated amorphous tissue (SiHx), with a variable volume fraction of nanocrystals dependent on the growth conditions [14,15]. In our previous papers [16,17], we reported the properties of PECVD poly-Si films deposited by changing the deposition temperature (Td) and film thickness. It was shown that the preferential orientation occurred in the range of Td higher than 500 TC, while the preferential orientation occurred at Td lower than 500 TC. In addition, we found no crystallization of the films at Td around both 150 and 650 'C. In this article, 0.2-Rm-thick nc-Si films were deposited using SiH 4 -H2 mixtures by changing Td. The effects of plasma-assisted hydrogenation at 300 °C on the optical and the structural properties were investigated for the nc-Si films. EXPERIMENTAL The samples were deposited by rf glow-discharge decomposition of SiH4-H2 mixtures in a hot-wall type fused quartz reactor, employing inductive coupling of rf power. The Sill4 and H2 flow rates were 1.0 and 3.0 sccm, respectively. The rf power (13.56 MHz) and gas pressure were 565 Mat. Res. Soc. Symp. Proc. Vol. 581 © 2000 Materials Research Society

maintained 20 W Torr,the respectively, and 0.2-•tm-thick filmsthewere Td