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Title: Second harmonic generation analysis in hydrogenated amorphous silicon nitride thin films

Abstract

Surface and interface electronic properties of plasma-deposited hydrogenated amorphous silicon nitride films have been investigated by means of optical second harmonic generation (SHG) technique. Polarization analysis shows that the nonlinear field origins from isotropic interfaces (film/substrate interface and film/air interface) whose spectral features are ascribed to surface/interface Si dangling bonds and strained Si-Si bonds. Differences and similarities with SHG spectra of pure amorphous silicon (a-Si:H) are discussed in terms of compositional inhomogeneities of the ternary alloy.

Authors:
; ; ; ;  [1];  [2]
  1. CNR-INFM Coherentia-Dipartimento di Scienze Fisiche, Universita di Napoli 'Federico II' Via Cintia, 80126 Naples (Italy)
  2. (Italy)
Publication Date:
OSTI Identifier:
20883264
Resource Type:
Journal Article
Resource Relation:
Journal Name: Applied Physics Letters; Journal Volume: 90; Journal Issue: 2; Other Information: DOI: 10.1063/1.2424661; (c) 2007 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; AIR; AMORPHOUS STATE; DEPOSITION; HARMONIC GENERATION; HYDROGEN; HYDROGENATION; INTERFACES; PLASMA; POLARIZATION; SILICON; SILICON NITRIDES; SUBSTRATES; TERNARY ALLOY SYSTEMS; THIN FILMS

Citation Formats

Lettieri, S., Merola, F., Maddalena, P., Ricciardi, C., Giorgis, F., and Dipartimento di Fisica, Laboratorio Materiali e Microsistemi, Politecnico di Torino C.so Duca degli Abruzzi 24, 10129 Turin. Second harmonic generation analysis in hydrogenated amorphous silicon nitride thin films. United States: N. p., 2007. Web. doi:10.1063/1.2424661.
Lettieri, S., Merola, F., Maddalena, P., Ricciardi, C., Giorgis, F., & Dipartimento di Fisica, Laboratorio Materiali e Microsistemi, Politecnico di Torino C.so Duca degli Abruzzi 24, 10129 Turin. Second harmonic generation analysis in hydrogenated amorphous silicon nitride thin films. United States. doi:10.1063/1.2424661.
Lettieri, S., Merola, F., Maddalena, P., Ricciardi, C., Giorgis, F., and Dipartimento di Fisica, Laboratorio Materiali e Microsistemi, Politecnico di Torino C.so Duca degli Abruzzi 24, 10129 Turin. Mon . "Second harmonic generation analysis in hydrogenated amorphous silicon nitride thin films". United States. doi:10.1063/1.2424661.
@article{osti_20883264,
title = {Second harmonic generation analysis in hydrogenated amorphous silicon nitride thin films},
author = {Lettieri, S. and Merola, F. and Maddalena, P. and Ricciardi, C. and Giorgis, F. and Dipartimento di Fisica, Laboratorio Materiali e Microsistemi, Politecnico di Torino C.so Duca degli Abruzzi 24, 10129 Turin},
abstractNote = {Surface and interface electronic properties of plasma-deposited hydrogenated amorphous silicon nitride films have been investigated by means of optical second harmonic generation (SHG) technique. Polarization analysis shows that the nonlinear field origins from isotropic interfaces (film/substrate interface and film/air interface) whose spectral features are ascribed to surface/interface Si dangling bonds and strained Si-Si bonds. Differences and similarities with SHG spectra of pure amorphous silicon (a-Si:H) are discussed in terms of compositional inhomogeneities of the ternary alloy.},
doi = {10.1063/1.2424661},
journal = {Applied Physics Letters},
number = 2,
volume = 90,
place = {United States},
year = {Mon Jan 08 00:00:00 EST 2007},
month = {Mon Jan 08 00:00:00 EST 2007}
}
  • We have investigated the effects of different post-deposition temperature anneals and N-H concentrations, on the generation of ultraviolet (UV)-induced two-coordinated nitrogen dangling bonds in plasma-enhanced chemical vapor deposited (PECVD) silicon nitride films using electron spin resonance (ESR). It is shown that the nitrogen dangling bond is activated by post-deposition anneals with temperatures as low as 500 {degree}C in N-rich PECVD nitride films followed by subsequent UV broadband illumination. It also appears that there is a possible correlation between the initial N-H concentration in the films and the concentration of generated nitrogen dangling bonds following the anneal/UV sequence. We also reportmore » the charge state associated with the nitrogen dangling bond using a combination of ESR and capacitance versus voltage measurements; these measurements suggest that this two-coordinated defect is electrically neutral when paramagnetic.« less
  • The optical dielectric function {epsilon} (1.5--6.5 eV), ir absorption (400--4000 cm{sup {minus}1}), and film density have been measured for a series of hydrogenated amorphous silicon nitride ({ital a}-Si{sub {ital x}}N{sub {ital y}}H{sub {ital z}}) films deposited at 400 {degree}C via rf plasma-enhanced chemical vapor deposition for varying (NH{sub 3})/(SiH{sub 4}) ratios {ital R}. From a detailed analysis of the ir and density results, the concentrations of Si-N, N-H, Si-H, and Si-Si bonds and of Si, N, and H atoms have been obtained for the films studied. An effective-medium-approximation analysis of the measured {epsilon} based on the Si-centered tetrahedron model presentedmore » in the preceding paper has provided a more sensitive means of determining the concentration of Si-Si bonds in the films and has demonstrated that careful measurements of {epsilon}{sub 1} and {epsilon}{sub 2} can serve as a useful probe of the bonding in these alloys. Approximately 9{times}10{sup 20} Si-Si bonds/cm{sup 3} have been found in N-rich films which are close in composition to silicon diimide, Si(NH){sub 2}, and these Si-Si bonds have been found to have a significant influence on both the optical energy gap {ital E}{sub opt} and the refractive index {ital n} of the films. New results obtained from the ir absorption measurements include the identification of (1) a shoulder near 1030 cm{sup {minus}1} on the main 880-cm{sup {minus}1} Si-N({ital s}) band and (2) a weak absorption feature near 640 cm{sup {minus}1} which is not hydrogen related. It has been found that the N-rich diimidelike films prepared here have very low porosities and are thermally stable up to 700 {degree}C, properties which will be important for their future applications.« less
  • Oblique angle deposited (OAD) silicon monoxide (SiO) thin films forming tilted columnar structures have been characterized by second-harmonic generation. It was found that OAD SiO leads to a rotationally anisotropic second-harmonic response, depending on the optical angle of incidence. A model for the observed dependence of the second-harmonic signal on optical angle of incidence allows extraction of the growth direction of OAD films. The optically determined growth directions show convincing agreement with cross-sectional scanning electron microscopy images. In addition to a powerful characterization tool, these results demonstrate the possibilities for designing nonlinear optical devices through SiO OAD.
  • We report results of electron paramagnetic resonance, photothermal deflection spectroscopy, and capacitance-voltage measurements on amorphous hydrogenated silicon nitride ({ital a}-SiN{sub {ital x}}:H) thin films exposed to ultraviolet (UV) illumination. It has been previously shown that exposure to UV light activates silicon dangling-bond defects, i.e., {ital K}{sup 0} centers, in {ital a}-SiN{sub {ital x}}:H thin films. Here, we demonstrate that the initially UV-activated {ital K}{sup 0} center can be irreversibly annihilated at long illumination times. Because this effect seems to scale with H content of the measured films, we propose that hydrogen may be passivating the {ital K}{sup 0} defects duringmore » the extended UV exposure. We also show that films subjected to long UV exposures trap charge as efficiently as those having much larger {ital K}{sup 0} concentrations. A few possibilities to explain this effect are discussed.« less