Enhanced photosensitivity in sol-gel derived 20GeO2:80SiO 2 thin films

Rajni, K. Pita, S. C. Tjin, Siu Fung Yu, C. H. Kam

Research output: Journal article publicationJournal articleAcademic researchpeer-review

10 Citations (Scopus)


We investigate the photosensitivity of binary 20GeO2:80SiO 2 (germanosilicate) inorganic films. The samples have been fabricated by the sol-gel spin-coating method and the densification has been performed by rapid thermal annealing at various temperatures ranging from 500 °C to 1000 °C. The -OH absorption bands in the Fourier-transform infrared (FTIR) spectra and the refractive-index data show that the films annealed below 900 °C are porous and the films annealed at 900 °C and above are dense. An ultraviolet (UV) KrF laser at 248 nm has been used to induce the change in the refractive index of the samples. We have achieved a large refractive-index change (Δn) of 0.0098 after UV illumination in excess of 1∈min for our dense germanosilicate films. This UV-induced refractive-index change is attributed to the formation of GeE'/SiE' centers from Ge-Ge/Si-Si (neutral oxygen monovacancy) and Ge2+ centers and to the creation of oxygen deficiency related defects. From our experiments, the oxygen deficiency related defects correspond to the absorption band at 620-740 cm-1 in the FTIR spectra and these are the defects which make a large contribution to Δn. The attenuation coefficient of the as-deposited and UV-illuminated dense samples is about 0.42 dB/cm at 1550 nm. For porous samples, UV exposure has densified the samples to some extent.
Original languageEnglish
Pages (from-to)535-541
Number of pages7
JournalApplied Physics A: Materials Science and Processing
Issue number3 SPEC. ISS.
Publication statusPublished - 1 Mar 2006
Externally publishedYes

ASJC Scopus subject areas

  • Chemistry(all)
  • Materials Science(all)


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