skip to main content

SciTech ConnectSciTech Connect

Title: Detailed photoluminescence studies of thin film Cu{sub 2}S for determination of quasi-Fermi level splitting and defect levels

We have studied chalcocite (Cu{sub 2}S) layers prepared by physical vapor deposition with varying deposition parameters by calibrated spectral photoluminescence (PL) and by confocal PL with lateral resolution of Δ x≈0.9 μm. Calibrated PL experiments as a function of temperature T and excitation fluxes were performed to obtain the absolute PL-yield and to calculate the splitting of the quasi-Fermi levels (QFLs) μ=E{sub f,n}−E{sub f,p} at an excitation flux equivalent to the AM 1.5 spectrum and the absorption coefficient α(ℏω), both in the temperature range of 20 K≤T≤400 K. The PL-spectra reveal two peaks at E{sub #1}=1.17 eV and E{sub #2}=1.3 eV. The samples show a QFL-splitting of μ>700 meV associated with a pseudo band gap of E{sub g}=1.25 eV. The high-energy peak shows an unexpected temperature behavior, namely, an increase of PL-yield with rising temperature at variance with the behavior of QFL-splitting that decreases with rising T. Our observations indicate that, contrary to common believe, it is not the PL-yield, but rather the QFL-splitting that is the comprehensive indicator of the quality of the excited state in an illuminated semiconductor. A further examination of the lateral variation of opto-electronic properties by confocal PL and the surface contour shows no detectable correlation between Cu{sub 2}S grains/grain boundaries and themore » PL-yield or QFL-splitting.« less
Authors:
; ;  [1] ; ; ;  [2]
  1. Institute of Physics, Carl von Ossietzky University Oldenburg, 26111 Oldenburg (Germany)
  2. Surface Science Division, Institute of Materials Science, Technische Universität Darmstadt, Petersenstraße 32, 64287 Darmstadt (Germany)
Publication Date:
OSTI Identifier:
22266123
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Applied Physics; Journal Volume: 114; Journal Issue: 23; Other Information: (c) 2013 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; ABSORPTION; COPPER SULFIDES; DEFECTS; EXCITATION; EXCITED STATES; FERMI LEVEL; GRAIN BOUNDARIES; PHOTOLUMINESCENCE; PHYSICAL VAPOR DEPOSITION; SEMICONDUCTOR MATERIALS; TEMPERATURE DEPENDENCE; THIN FILMS; YIELDS