1H Nmr in μc-Si:H Deposited With Different Plasma Excitation Frequencies and Silane Concentrations

Abstract

AbstractSix samples of pc-Si:H were prepared by PECVD at 200°C with plasma excitation frequencies ranging from 13 MHz to 95 MHz. Four samples were prepared with gas mixtures of 3% SiH 4 in H2. For these samples the plasma excitation frequencies ranged from 13 MHz to 95 MHz. Two samples at a plasma excitation frequency of 95 MHz were prepared at 5% and 8% SiH4 in H2. All samples were deposited on aluminum foil and etched off using dilute HCI to form powdered samples. These samples were studied by nuclear magnetic resonance (NMR), electron spin resonance (ESR) and infrared (IR) absorption measurements. The broad and narrow components of the free induction decay (FID) in the NMR measurements were compared to the respective components that occur in a-Si:H. The broad components in the various samples of μc-Si:H are similar in width to the broad component in a-Si:H, but the narrow component is narrower by a factor of two as compared to the narrow components in μ-Si:H. The narrow component in pic-Si:H samples exhibits a beat pattern similar to a previously observed Pake doublet. ESR measurements performed between 20 K and 300 K show that the spin densities, which can be attributed to silicon dangling bond states, increase as a function of plasma excitation frequency. The hydrogen content of each μc-Si:H sample was estimated from the NMR measurements, and these estimates are in good arrangement with the hydrogen content estimated from IR measurements.