Origin of band-A emission in diamond thin films

By means of scanning cathodoluminescence (CL) measurements, high-resolution transmission electron microscopy (HRTEM), and electron energy loss spectroscopy (EELS), we have studied the origin of the band-A emission in homoepitaxial diamond thin films grown using microwave-plasma chemical vapor deposition (CVD). A broad luminescence peak at around 2.9 eV, the band-A emission, was observed in homoepitaxial diamond films with nonepitaxial crystallites (NC's), but not in the high-quality films without NC's. The scanning CL measurements showed that the band-A emission appeared only at NC sites. TEM revealed that the NC's contained defects such as dislocations and several types of grain boundary (GB). Further, HRTEM indicated that several types of incoherent GB existed within the NC's including five-, six-, and seven-member carbon atom rings. These were the same GB's as those in polycrystalline CVD diamond films that had sp2-like structure of carbon atoms as indicated by the observation of the 1s-π signal in EELS. It is then reasonable to consider that, if sp2-like structures behave as defects in the network of sp3 structure of diamond, one possible origin of band-A emission might be the sp2 defects in the GB's and dislocations. The band-A emission behavior in homoepitaxial CVD diamond films is the same as that in polycrystalline diamond films. The origin of the band-A emission generally observed in many kinds of CVD diamond is discussed relative to these results

SCANNING ISOTHERMAL CURRENT TRANSIENT SPECTROSCOPY (SICTS) FOR DEEP LEVEL CHARACTERIZATION

We reported Isothermal Capacitance Transient Spectroscopy (ICTS), with which deep level signals can be obtained spectroscopically under isothermal condition. ICTS was applied to the measurement of deep states in amorphous and crystalline semiconductors. This method has an advantage : measurements are made at constant temperature. Therefore, this method is considered to be more suitable for the microscopic spatial characterization than scanning DLTS

ISOTHERMAL CAPACITANCE TRANSIENT SPECTROSCOPY : ITS APPLICATION TO THE STUDY OF GAP STATES OF a-Si:H

A basic idea of ICTS (Isothermal Capacitance Transient Spectroscopy) for a system of continuously-distributed gap state and experimental data by the ICTS applied to P-doped a-Si:H Schottky barrier diode are presented. It is shown that the ICTS is a useful tool for the study of gap state of a-Si:H whose material parameters are strongly temperature-dependent

ANNEALING STUDIES ON LOW OPTICAL ABSORPTION OF GD a-Si:H USING PHOTOACOUSTIC SPECTROSCOPY

We have performed photoacoustic spectroscopy (PAS), ESR and ir absorption measurements on undoped GD a-Si:H film before and after isochronal annealings, from which absorption coefficient (down to α = 1 cm-1), spin density (Ns) and bonded H content (CH) were determined. It has been found out that the extraporated spectrum of spin-free a-Si:H shows a long exponential tail, and that additional broad absorption is strongly correlated with Ns. The origin of α below Eo is discussed