The goal of the work is the pulsed laser deposition (PLD) of CdTe, CdSe and ZnTe thin films with low-power laser pulses, as well as the investigation of the structural properties of thus obtained films. The PLD apparatus used in our experiments is described in detail elsewhere [1]. For the present purpose, it was supplied with a quadrupole mass spectrometer (QMS, HALO 301, Hiden Analytical) equipped with a pulse ion counter. The action of QMS has been synchronized with the laser action by a specially designed electronic device. With this improvement, the vapour cloud ejected from the target by a laser pulse, arrives at the spectrometer head in a right time to be analysed on chemical composition. This improvement enables also performing time–of–flight (TOF) experiments, from which the velocity distribution of the laser emitted particles is determined.

In our experiments we used a YAG:Nd laser operating with a 25 Hz pulse frequency. The pulse energy density on the target surface was 1.9 J/cm² or 2.3 J/cm² and the pulse duration was 100 ms. The targets were CdTe, CdSe, or ZnTe tablets of diameter of 2 cm made of the corresponding powdered materials pressed at the pressure of 700 atm. The films were deposited onto glass and GaAs(001) substrates held at 200°C. The film thickness ranged from 0.17 µm (CdTe) to 0.55 µm (CdSe).

The film surface appearance was studied with optic and atomic force microscopy. These investigation showed that at the low energy pulses used, the number of particularities incorporated into the films, which usually deteriorate the film quality, is very small. Otherwise, the film surfaces were very smooth and consisted of flat crystallites. However, the films on the GaAs substrates showed a more crystalline (better developed) form. The X–ray investigations revealed that all films were strongly textured in the (111) or (001) planes. Therefore, these preliminary results show that the preparation method adopted is very promising in preparing thin films of A^IIB^VI compounds and their composed structures.

The TOF measurements performed for all kinds of the emitted particles (atomic A^II and B^VI and diatomic B₂^VI species) showed that their velocity distributions are those of the Maxwellian–on–stream distribution, i. e. the distributions are considerably narrower than the classic Maxwellian distribution. Moreover, all the species for a given compound had roughly the same velocity distribution, i. e. they arrived to the substrate roughly at the same time. The average velocity was of the order 800 m/s. These properties are beneficial for the preparation of high quality stoichiometric thin films. It is worthy to note that the TOF measurements for CdTe, CdSe and ZnTe were performed for the first time.

1. M. Oszwaldowski, T. Berus, P. Sydorchuk, J. Rzeszutek, Rev. Sci. Instrum., 74 (2003) 3160.

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