L. Lassabatere

Comparative studies between the growth characteristics of Bi2Te3 thin films deposited on SiO2, Si(100) and Si(111)

Thin films of Bi2Te3 on SiO2, Si(100) and Si(111) were deposited using a hot wall epitaxy (HWE) system. The growth conditions were optimized by the criterion of the highest mobility. XRD and SEM analysis show that the films obtained were stoichiometric and present a good morphology. No difference was observed between layers deposited on Si(100) and on Si(111): the layers were not sensitive to the initial orientation of silicon. The electrical measurements performed at room temperature show that the quality of layers deposited on SiO2 was better than the quality of layers deposited on Si(100) and Si(111). The figure of merit obtained in the case of the SiO2 substrate was Z = 1.9 × 10−3K−1, which is close to those reported for the monocrystal. The study of the first growing stage shows that the difference obtained between the substrates can be explained by the degree of reactivity of their surfaces.

Chemical preparation of GaSb (001) substrates prior to MBE

The chemical preparation of GaSb(001) substrates was performed by Br2-HCl-HNO3-CH3COOH solution. The removed layer thickness was evaluated as a function of the constituent concentrations and the etching time. The surface quality was controlled by SEM, RHEED and AES. With this treatment, excellent surface morphology of substrates and growth film is obtained.

Study of GaSb(001) substrate chemical etching for molecular‐beam epitaxy

In this paper we present and discuss the surface properties of GaSb substrates correlated to the cleaning procedure. Different etchants were tested and the resulting surfaces were studied by Auger spectroscopy, then by reflection high‐energy electron diffraction and finally annealed under an Sb4 flux in order to get a suitable substrate for molecular‐beam epitaxy. From the comparison of the surface properties we show that one of the tested etchants, which associates HCl, HBr, CH3COOH, and HNO3 gives the best results: the etch rate can easily be controlled, the cleaned surfaces are smooth (i.e., free of etch pits) and the surface stoichiometry is the least disturbed by the cleaning procedure.

UV and ozone cleaning of GaSb (100) surfaces prior to MBE growth

Abstract The formation of sacrificial oxides by UV-ozone exposure on GaAs and InP is a well established procedure in the preparation of clean substrates for MBE growth. We describe a UV-ozone treatment used to prepare GaSb (100) substrates and report results obtained by Auger (Auger electron spectroscopy) which show that the quality of the so prepared substrates is excellent for MBE (molecular beam epitaxy).

Sb-capping and decapping of MBE-grown GaSb(100)

Abstract We present a study of GaSb(100) surfaces grown by molecular beam epitaxy, protected by an Sb cap during ambient storage, and annealed in ultra-high vacuum. The surface structure, composition and electronic transitions are investigated with low energy electron diffraction, Auger electron spectroscopy, and electron energy loss spectroscopy. Successful Sb-decapping is achieved by annealing at 300° C for 30 min. It leads to a (2 × 3)−c(2 × 6) reconstructed surface with less residual damage and higher Sb concentration than surfaces prepared by sputtering and annealing.

Modification of GaSb(100) surfaces induced by annealing under vacuum and under Sb4 and As4 flux

Abstract We present Auger and RHEED studies of the modifications of GaSb(100) molecular beam epitaxy (MBE) surfaces induced by annealing, under vacuum and under Sb 4 or As 4 flux. After annealing under vacuum, in the 250–400°C temperature range, Auger peaks and RHEED intensity show modifications of the atoms arrangements and concentrations in the surface layer. Above 400–420°C Sb desorption results in noticeable changes of the surface stoichiometry and structure characterized, for T > 500°C, by the formation of Ga droplets. Under normal growth conditions the GaSb surface presents a (1 × 3) reconstruction. Annealing under Sb 4 flux induces the formation of (1 × 5) or (2 × 5) reconstructions. Annealing under As 4 flux leads, for T T > 450°C, to the desorption of Sb atoms accompanied by the formation of GaAsSb microphases.

GaSb molecular beam epitaxy growth on vicinal surfaces studied by RHEED

The growth of GaSb on vicinal surfaces has been studied by measuring the RHEED intensity. On a (001) GaSb surface 2° misoriented towards the [010] direction (commonly noted C type surface) and for a Ga flux in the range of 1014 atoms cm−2 s−1, we have observed around 410°C, that the growth mode changes from 2D nucleation to step propagation. This temperature is lower than that reported on GaAs and has been interpreted by an easier diffusion of gallium adatoms on GaSb than on GaAs. In order to study the effect of surface anisotropy, growth mode transition temperatures were determined during the growth on a (001) GaSb surface 1° misoriented towards the [110] and [110] directions as a function of the SbGa flux ratio. The results were analyzed both from adatom diffusion and kinetics of adatom sticking on steps.

UV-O3 preparation of InAs (100) surfaces prior to MBE growth

Abstract InAs (100) surfaces cleaned by the UV-ozone method or by Br-MeOH etching were annealed under an As flux. By Auger electron spectroscopy (AES) and reflection high energy electron diffraction (RHEED), we compare the quality of these surfaces before and after annealing. We show that the UV-ozone process, unlike Br-MeOH etching, produces a capping oxide which desorbs. We study this desorption as a function of temperature and show that, at 510°C, the layer is removed. The surface is then oxygen and carbon free. It is therefore more appropriate for growth than the surface obtained by Br-MeOH etching, which is always contaminated by carbon.

Reflection high energy electron diffraction intensity modifications induced by antimony flux interruption during GaSb growth by molecular beam epitaxy

Abstract While in the case of growth of GaAs or As compounds several surface structures are frequently encountered, in the case of GaSb and Sb compounds RHEED studies mainly show, under normal growth conditions, a (1 × 3) structure. This structure, associated to a particular surface arrangement proposed by Franklin et al. [Phys. Rev. B 18 (1990) 12619], can be used to explain Ga and Sb atoms incorporation during GaSb growth. In this paper we first study and analyse the evolution of the RHEED intensity when, starting from normal growth conditions, the antimony flux is stopped. Then we propose a model describing the evolution of the atomic surface arrangement during gallium deposition.