Magyar Tudományos Akadémia
(SZFKI & JILA)
Threshold ionization mass spectroscopy of radicals in radiofrequency (RF) SiH4 and H2-SiH4 plasmas
Hydrogenated amorphous (a-Si:H) and microcrystalline (μc-Si:H) silicon, and their carbon and germanium alloys, are used for most large-area semiconductor devices, such as liquid-crystal displays and photovoltaic devices. These thin films are deposited from the hydrogenated molecular gases of Si, C and Ge and dopants P and B (e.g. SiH4). The molecular dissociations that yields this “chemical vapor deposition” is initiated by DC, RF, VHF or microwave discharge, or a high-temperature “hot-wire” surface. Neutral radicals yield most film growth, but cations and very small Si particles also contribute to the growth of the semiconductor film. The continual quest for improved device properties motivates studies of the discharge physics and deposition chemistry.
In my presentation I report studies of neutral radical species at the substrate during RF-discharge deposition of a-Si:H from SiH4 and H2-SiH4 mixture. We use threshold ionization mass spectroscopy (TIMS) to measure the radicals, since this method can identify minor amounts of all the SixHy radicals in the presence of their stable parent gases (SixH2x+2). Unlike optical methods, TIMS measures radical densities at the substrate surface, where they contribute to film growth. Besides detailed explanation of the experimental method I will also give a brief overview of Si-based photovoltaic materials. The experiments presented here were carried out in JILA, University of Colorado at Boulder, and will be included in my PhD thesis.
A szeminárium egyben munkabeszámoló is!
2005. szeptember 20. (kedd) 10:00
I. épület Tanácsterem
Minden érdeklődőt szívesen látunk!