Laser-induced optical changes in amorphous multilayers

Abstract

It is shown that the well-known blue-shift of the fundamental absorption edge in as-deposited compositionally modulated amorphous Si/Ge and As 6 Se 94 /Se 80 Te 20 multilayers (with periods of 4-8 nm) is further enhanced due to the thermal or laser-induced intermixing of adjacent layers.The laser-induced intermixing process, as supported by experiments and model calculations, can be attributed to both the local heating and photo-effects in As 6 Se 94 /Se 80 Te 20 multilayers, while only the thermal effects were observed for Si/Ge multilayers. Structural transformations, based on this enhanced interdiffusion, provides good capability for spatially patterning optoelectronic devices and digital information recording. a) Corresponding author.

Kinetics and chemical analysis of photoinduced interdiffusion in nanolayered Se/As2S3 films

“…[1][2][3] These amorphous nanolayered chalcogenide ͑ANC͒ structures are similar to the crystalline superlattices yet distinct from ideal crystalline superlattices produced by molecular beam epitaxy. The ANCs can be considered as well-correlated layers with good periodicity and smooth interface.…”

“…We have expected only photobleaching effect during irradiation because of the following two reasons: ͑1͒ any photoinduced diffusion of Se into As 2 S 3 should increase the bandgap 3 and ͑2͒ the decrease in Se thickness by photoinduced diffusion favors an increase in bandgap due to quantum size effects. 1,2 The top of the valence band in this multilayered film stack is formed by the nonbonding orbitals of the Se atoms. Change in the position of Se atoms due to new bond formation causes a change in interaction between the lone pair electrons, which in turn changes the forbidden gap.…”

“…2,4 For example, photoinduced diffusion in short period multilayer systems is important because of its potential applications in holographic recording and fabrication of phase gratings. 1 In spite of its practical usefulness, the mechanism of photoinduced diffusion is not properly understood.…”

Observation of three-photon absorption and saturation of two-photon absorption in amorphous nanolayered Se/As2S3 thin film structures

“…Recently chalcogenide glasses were prepared in the form of high quality multilayers with nanomodulation and established the possibilities for tailoring the optical properties. 4 These amorphous nanolayered chalcogenide structures ͑ANC͒ are similar to the crystalline superlattices, but it is difficult to imagine such structures as ideal crystalline superlattices produced by molecular beam epitaxy. But the ANCs can be considered as well correlated layers with good periodicity, smooth interface, and good surface roughness.…”

“…Traditional spectroscopic studies such as optical absorption, photoluminescence, and x-ray photoelectron spectroscopy on ANCs indicate that these materials can be used in micro-and optoelectronics. 4,5 However, there are not many reports about the nonlinear optical properties of the ANCs despite the considerable interests in photoinduced phenomena. 6 In this article we report the optical and nonlinear optical absorption of amorphous nanomultilayered Se/ As 2 S 3 film on a glass substrate prepared by the conventional thermal evaporation technique.…”