Accession Number:

ADP011517

Title:

Light Induced Changes in the Optical Properties of Thin As - S - Ge(Bi, Tl) Films

Descriptive Note:

Corporate Author:

BULGARIAN ACADEMY OF SCIENCES SOFIA (BULGARIA) CENTRAL LAB OF PHOTOPROCESSES

Personal Author(s):

Report Date:

2001-06-01

Pagination or Media Count:

7.0

Abstract:

In this paper we report results from studying changes in the optical properties of thin vacuum deposited films from the systems As40-xGexS60 0- x - 40 and As2S3100-xBiTIx 0 - x - 15 depending on the composition and conditions of evaporation and illumination to light. The optical transmission and reflection of thin layers deposited on BK-7 optical glass substrates have been measured in the spectral region of 350 - 1500 nm and the refractive indices and optical band gap Eg were calculated. It was found that the method of evaporation influences considerably the properties of thin chalcogenide films, The addition of Bi or TI in As2S3 leads to an increase in the refractive index while Ge causes its decreasing. The illumination of as- deposited films leads to an effect of photodarkening and decreasing in the optical band gap for As-containing films and photobleaching for As - Ge - S layers. Using TRRm methods R is the reflection of 100 nm thick films deposited on Si substrate, the thickness of very thin layers from the systems As - S and As - S - Ge have been determined to an accuracy of 2 nm. At the same time, the accuracy in the determination of the refractive index, n, was less than -0.005 For the absorption coefficient, k, around the absorption edge, it was about -0.01, using a combination of TRRm and TR methods. A comparison between the results obtained from the spectrophotometric and ellipsometric measurements has been made.

Subject Categories:

  • Electrooptical and Optoelectronic Devices
  • Ceramics, Refractories and Glass
  • Optics

Distribution Statement:

APPROVED FOR PUBLIC RELEASE