Defect Creation by Electron Beam Irradiation in Amorphous Silicon Nitride Films Compared with That by Light Soaking
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Defect Creation by Electron Beam Irradiation in Amorphous Silicon Nitride Films Compared with That by Light Soaking Tatsuo Shimizu, Yuji Kawashima, and Minoru Kumeda Department of Electrical and Electronic Engineering, Kanazawa University, Kanazawa 920-8667, Japan ABSTRACT
Defect creation by electron beam irradiation is compared with that by light soaking in a-Si1-xNx:H films. For the film with x=0.06, the ESR spin density increases by 20-keV electron beam irradiation without changes in the g-value. However, for the film with x=0.47, the ESR spin density increases with accompanying the decrease in the g-value from 2.0042 to 2.0034. The decrease in the g-value can be explained by increasing number of N atoms at the backbond site of the Si atom having the dangling bond. Light soakings does not change the g-value of the ESR signals of the films. INTRODUCTION
The mechanism of metastable dangling-bond (DB) defects creation in a-Si:H and related alloy films is an important issue for clarifying the origin of the Staebler-Wronski effect [1]. It is well known that the intensity of the ESR signal due to Si DBs increases by light soaking (LS) [2]. The increased ESR signal has the same shape, linewidth and g-value as those before LS. It is interesting to compare the DB-creation mechanism for LS with that by electron-beam (EB) irradiation [3]. In the present study, we found that the g-value for DBs created by EB irradiation is smaller than that for original DBs in a-Si1-xNx:H with a large x while the g-value for DBs created by LS is the same as that for original DBs. Both the g-values for DBs created by EB irradiation and LS are the same as those for original DBs in a-Si:H and a-Si1-xNx:H with a small x. SAMPLE PREPARATION AND CHARACTERIZATION METHODS
a-Si1-xNx:H films are prepared by glow discharge decomposition of SiH4 and NH3 or N2 at a nominal temperature of 350 °C (the actual temperature is expected to be between 250 °C and 300 °C). The films were deposited on substrates of silica glass for ESR and optical measurements and highly resistive Si crystals for IR measurements. The N content was determined by electron probe micro analysis (EPMA), and the H content was determined by Fourier transformed infrared absorption (the contents of H atoms bonded to Si and N are separately determined). The optical gap is deduced from the Tauc relation using the results of optical transmission measurements. X-band ESR measurements were carried out both at room temperature and liquid nitrogen temperature. A high-pressure
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mercury lamp coupled with a band pass filter of CuSO4 (photon energies of 2.2 –4.0 eV) with a power density of 200 mW/cm2 was used for LS for the film with x = 0.47, while a Xe lamp coupled with an IR cut filter with a power density of 3.2 W/cm2 was used for the films with x = 0.06 and 0 by taking into account different optical gaps. EB irradiation was done using EPMA apparatus. The sample was scanned during the irradiation of EB with a diameter of 40 microns. The EB dose Q is defined as the total energy d
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