Ablation of 2-6 Compounds with Low Power Pulses of YAG:Nd Laser

Abstract

The 2-6 compounds and their mixed crystals are important semiconductor materials with practical applications in various areas of solid state electronics and optoelectronics. Most of the applications need these materials in a thin film form. One of the most versatile methods of obtaining thin films and their composed structures is the Pulsed Laser Deposition (PLD) method. That method has been used many times to the deposition of the 2-6 compound films and the result of the investigations of both the target ablation process and the obtained films physical properties were published in numerous publications. The earlier publications have been summarized in several excellent reviews (Cheung & Sankur, 1988; Christley & Hubler, 1994; Dubowski, 1991). In spite of the existing broad experimental material, optimum technological conditions for obtaining 2-6 compound layers by PLD with predefined properties has not as yet been determined. This is because the layers properties depend on the Pulsed Laser Ablation (PLA) process of the target material. The ablation depends on such parameters of the process as: the energy and duration of the laser pulse, pulse repetition frequency and the angle of incidence, target preparation method and some others. Therefore, the PLA is a multi-parameters process. It has been recently shown (Rzeszutek et al., 2008a,b) that pulsed laser ablation of CdTe target with low power pulses of YAG:Nd laser can be an effective method for the deposition of high quality CdTe thin films. The advantages of using low-power pulses of YAG:Nd laser for the CdTe ablation are following. The YAG:Nd laser is as such a very stable and environmentally harmless laser that can be very easy handled. Because the thermal evaporation of CdTe results in nearly congruent vaporisation of Cd and Te (Ignatowicz S. & A. Koblendza 1990), it may be expected that the low power pulsed laser ablation should be a very effective method of the deposition of CdTe thin films. However, the most important reason that ablation is performed in the low-power regime, realized by long pulse duration of 100 μs, is to minimize the splashing effect that is the effect of emitting of macroscopic particularities from the target (Cheung & Sankur, 1988). That degrades the quality of the thin films obtained by the laser ablation. Therefore, the type of the laser and its pulse duration time are dictated by practical reasons. In this chapter we summarize our earlier experiments on the ablation of CdTe and add new results on the ablation of CdSe and ZnTe not as yet published. Like CdTe, these two latter compounds, are rather volatile materials, and the use of the low-power YAG:Nd laser ablation for their thin film preparation can be substantiated largely in the same way as it is