Photo-crystallization in a-Se imaging targets: Raman studies of competing effects

Similarities in the kinetics of photocrystallization and photodarkening in a-Se

“…The thermal behavior of the t-Se growth exhibits distinct regimes that reflect the temperature dependences of the onset time on , and the initial rate of crystal growth after onset ͑df c / dt͒ o . As found in our earlier work: 11 occur in the range of 260-302 K, and above 318 K. In the former regime, the rate is T-independent with the value ͑df c / dt͒ o Ϸ 0.09 h −1 , and in the latter regime ͑df c / dt͒ o increases with temperature.…”

“…11 we show that the nucleation model of Stephens and co-workers 12 allows an understanding of the thermal behavior of ͑df c / dt͒ o in terms of the competition between viscosity and strain in the secondary growth of t-Se nuclei. For 260-302 K, ͑df c / dt͒ o is driven by the constant strain field arising from the 13% t-Se/ a-Se density discontinuity, and ͑df c / dt͒ o is T-independent.…”

“…4,8,9 Our earlier work demonstrated that both PC and an irreversible PD component 10 are absent in a-Se films within a small temperature range close to T g , while both processes are pronounced at lower temperatures. 8,11 In the case of PC, it was concluded that the competition of strain and viscosity strongly suppresses the secondary (i.e., macroscopic) growth of crystalline domains, according to a 1980 model by Stephens and co-workers. 12 This letter discusses recent observations that link the kinetic behavior of PC during the primary growth of crystalline domains ͑i.e., prior to reaching the minimum nucleation size͒ with the kinetics of irreversible photodarkening ͑IPD͒ at temperatures below T g .…”

“…[13][14][15] We investigate PC in a-Se HARP targets at temperatures of 250-337 K under exposure to 17 W / cm 2 of 633 nm ͑1.96 eV͒ light from a HeNe laser. 11 The PC is detected by Raman spectroscopy measured using the same laser beam. The HARP samples are ϳ15 m a-Se films deposited on glass with thin blocking layers ͑ϳ0.05 m͒ that do not interfere with the Se spectra.…”

Photoinduced bond breaking in a‐Se: Raman spectroscopic study

“…2. Other experiments reported also a significant and broad Raman peak around 250 cm -1 wavenumber [10][11][12]. In the following the sample was illuminated with the Ar ion laser for 10 minutes.…”