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Title: Effects of temperature and near-substrate plasma density on the structural and electrical properties of dc sputtered germanium thin films

Abstract

Germanium thin films were deposited by dc reactive magnetron sputtering as a function of substrate temperature and ion flux using an unbalanced magnetron with an external magnetic field. The ion flux and energy distribution were measured using a retarding field energy analyzer (RFEA), a flat probe with a guard ring, and cylindrical Langmuir probes. The RFEA ion flux, the flat probe saturation currents, and the ion densities inferred from the cylindrical probe data are in very good agreement over a wide range of plasma densities, which were varied both by the external coil current and discharge power. The RFEA ion energy distributions are in good agreement with the plasma potentials inferred from the cylindrical probes, and suggest that the nonuniformity of the plasma in the vicinity of the substrate holder should be considered in the interpretation of probe results in these systems. The deposited films were characterized by x-ray diffraction, Raman spectroscopy, optical transmission, resistivity, and Hall effect measurements. Under low ion bombardment conditions, an abrupt onset of the crystalline phase with respect to temperature is observed in the Raman and x-ray diffraction measurements, and the crystal quality increases with increasing temperature above the transition temperature. The transition is alsomore » accompanied by a sharp decrease in film resistivity. The microcrystalline films have a strong preferential orientation in the (220) direction, and are p type with carrier densities in the range 10{sup 18} cm{sup -3} and mobilities in the range 15-30 cm{sup 2}/V-s. The structural and electronic properties of the films are sensitive to the ion flux. Near the transition temperature the effects of increasing ion flux can be attributed to the small temperature rise that accompanies the higher plasma density. At higher temperatures the increased ion flux results in a more random crystallographic orientation, with significantly lower carrier concentrations and only slightly lower carrier mobilities, implying either a reduction in acceptor defect density and/or the creation of compensating n-type defects.« less

Authors:
; ; ;  [1]
  1. Department of Physics and Astronomy, Macalester College, St. Paul, Minnesota 55105 (United States)
Publication Date:
OSTI Identifier:
22051357
Resource Type:
Journal Article
Journal Name:
Journal of Vacuum Science and Technology. A, International Journal Devoted to Vacuum, Surfaces, and Films
Additional Journal Information:
Journal Volume: 29; Journal Issue: 5; Other Information: (c) 2011 American Vacuum Society; Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 1553-1813
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; 36 MATERIALS SCIENCE; CARRIER DENSITY; CARRIER MOBILITY; CRYSTALLOGRAPHY; CYLINDRICAL CONFIGURATION; ELECTRIC CONDUCTIVITY; ENERGY SPECTRA; GERMANIUM; HALL EFFECT; ION BEAMS; ION DENSITY; LANGMUIR PROBE; LIGHT TRANSMISSION; MAGNETIC FIELDS; MAGNETRONS; PLASMA DENSITY; RAMAN SPECTROSCOPY; SPUTTERING; THIN FILMS; TRANSITION TEMPERATURE; X-RAY DIFFRACTION

Citation Formats

Pollock, Kristin M., Kaufman-Osborn, Tobin, Hiltrop, Jonas, and Doyle, James R. Effects of temperature and near-substrate plasma density on the structural and electrical properties of dc sputtered germanium thin films. United States: N. p., 2011. Web. doi:10.1116/1.3607410.
Pollock, Kristin M., Kaufman-Osborn, Tobin, Hiltrop, Jonas, & Doyle, James R. Effects of temperature and near-substrate plasma density on the structural and electrical properties of dc sputtered germanium thin films. United States. doi:10.1116/1.3607410.
Pollock, Kristin M., Kaufman-Osborn, Tobin, Hiltrop, Jonas, and Doyle, James R. Thu . "Effects of temperature and near-substrate plasma density on the structural and electrical properties of dc sputtered germanium thin films". United States. doi:10.1116/1.3607410.
@article{osti_22051357,
title = {Effects of temperature and near-substrate plasma density on the structural and electrical properties of dc sputtered germanium thin films},
author = {Pollock, Kristin M. and Kaufman-Osborn, Tobin and Hiltrop, Jonas and Doyle, James R.},
abstractNote = {Germanium thin films were deposited by dc reactive magnetron sputtering as a function of substrate temperature and ion flux using an unbalanced magnetron with an external magnetic field. The ion flux and energy distribution were measured using a retarding field energy analyzer (RFEA), a flat probe with a guard ring, and cylindrical Langmuir probes. The RFEA ion flux, the flat probe saturation currents, and the ion densities inferred from the cylindrical probe data are in very good agreement over a wide range of plasma densities, which were varied both by the external coil current and discharge power. The RFEA ion energy distributions are in good agreement with the plasma potentials inferred from the cylindrical probes, and suggest that the nonuniformity of the plasma in the vicinity of the substrate holder should be considered in the interpretation of probe results in these systems. The deposited films were characterized by x-ray diffraction, Raman spectroscopy, optical transmission, resistivity, and Hall effect measurements. Under low ion bombardment conditions, an abrupt onset of the crystalline phase with respect to temperature is observed in the Raman and x-ray diffraction measurements, and the crystal quality increases with increasing temperature above the transition temperature. The transition is also accompanied by a sharp decrease in film resistivity. The microcrystalline films have a strong preferential orientation in the (220) direction, and are p type with carrier densities in the range 10{sup 18} cm{sup -3} and mobilities in the range 15-30 cm{sup 2}/V-s. The structural and electronic properties of the films are sensitive to the ion flux. Near the transition temperature the effects of increasing ion flux can be attributed to the small temperature rise that accompanies the higher plasma density. At higher temperatures the increased ion flux results in a more random crystallographic orientation, with significantly lower carrier concentrations and only slightly lower carrier mobilities, implying either a reduction in acceptor defect density and/or the creation of compensating n-type defects.},
doi = {10.1116/1.3607410},
journal = {Journal of Vacuum Science and Technology. A, International Journal Devoted to Vacuum, Surfaces, and Films},
issn = {1553-1813},
number = 5,
volume = 29,
place = {United States},
year = {2011},
month = {9}
}