Kunimaro Tanaka

Energy location of ESR hyperfine centers of P-doped a-Si:H

Abstract ESR hyperfine spectra are investigated in P-doped a-Si:H (1-% PH 3 /SiH 4 ) deposited on the substrates of different temperatures (300°C and room temperature). Similar hyperfine spectra are observed in both samples in spite of large difference in the Fermi energy level between two, suggesting that the spin centers with the hyperfine coupling are energetically distributed at least down to the midgap.

ENDOR and ESEEM study of phosphorus-doped a-Si:H

Abstract Hyperfine interactions due to the electron nuclear dipolar coupling between an electron spin and nearby nuclear spins (29Si, 31P) in P-doped a-Si:H films (PH3/SiH4 = 1 %) were detected for the first time by electron-nuclear double resonance (ENDOR) and electron spin echo envelope modulation (ESEEM) measurements. The nature of a spin center with g ∼ 2.0043 is discussed on the basis of the experimental results.

Direct evidence for strong electron-phonon interaction on deep trapping process in P-doped a-Si:H

Abstract We report the first direct evidence for a strong electron-phonon coupling on carrier capture process in a-Si:H. Results on the low-energy luminescence transition induced by the below-bandgap excitation (h v = 1.17 eV and h v = 0.94 eV) and the below-bandgap optical absorption spectrum of P-doped a-Si:H lead to a strong indication that (1) the low-energy PL band originates from the deexcitation of an electron from the conduction band edge to the defect states and (2) this process is predominated by a strong electron-phonon coupling with a Franck-Condon shift of about 0.28 eV at 77 K.

Measurement of spatial distribution of gap states originating from dangling bonds near metal/a-Si:H interface

Abstract The density of the gap states originating from the dangling bonds was measured as a function of the distance from the interface of metal/a-Si:H using the isothermal capacitance transient spectroscopy (ICTS) as well as the C - V analysis on the Schottky barriers. The results show that the density of dangling bonds takes a maximum at around 1000A depending on a doping level of P atoms.

1H-ENDOR-detected ESR spectra of P- and B-dope a-Si:H

Abstract Highly-resolved ESR spectra of B- and P-doped a-Si:H have been determined using a 1H-ENDOR(electron-doubled-resonance_-detected ESR, from which it is speculated that a major fraction of spin centers in B-doped a-Si:H is not coupled with B or the coupling is very weak, which is much different from the electron spin system coupled with P atoms in P-doped a-Si:H.