MOCVD growth of Bi2Te3-Sb2Te3 layers : Effect of growth parameters on the electrical and thermoelectrical properties

The growth of (Bi1-xSbx)2Te3 thin films by metal-organic chemical vapour deposition (MOCVD) using trimethylbismuth, triethylantimony and diethyltellurium as bismuth, antimony and tellurium sources respectively is investigated on pyrex substrates. The electrical and thermoelectrical properties of this material are also measured over the growth temperature range 360-470°C. The studies are also made on the effect of VI/V ratio on these properties in the variation range 2-9. Polycrystalline structure is confirmed by X-ray diffraction, and it is observed that the intensity of the preferred orientation is higher at 450°C. The measurement of Seebeck coefficient shows that all samples have p-type conduction. The best value of this parameter is obtained for high growth temperature (240µV/K). The good result obtained for (Bi1-xSbx)2Te3 thin films revealed the great potential of MOCVD method which is an industrial technique to produce good materials for device applications (sensors and thermopiles).The growth of (Bi1-xSbx)2Te3 thin films by metal-organic chemical vapour deposition (MOCVD) using trimethylbismuth, triethylantimony and diethyltellurium as bismuth, antimony and tellurium sources respectively is investigated on pyrex substrates. The electrical and thermoelectrical properties of this material are also measured over the growth temperature range 360-470°C. The studies are also made on the effect of VI/V ratio on these properties in the variation range 2-9. Polycrystalline structure is confirmed by X-ray diffraction, and it is observed that the intensity of the preferred orientation is higher at 450°C. The measurement of Seebeck coefficient shows that all samples have p-type conduction. The best value of this parameter is obtained for high growth temperature (240µV/K). The good result obtained for (Bi1-xSbx)2Te3 thin films revealed the great potential of MOCVD method which is an industrial technique to produce good materials for device applications (sensors and thermopiles)

Two-Phase Pulsed Flow of a Non Newtonian Fluid in Pipe with Elastic Wall

K. Gueraoui Team of modelling in fluid mechanics and environment, LPT, URAC 13 Faculty of sciences, Mohamme

Elaboration and characterization of MOCVD (Bi1-x Sbx)2 Te3 thin films

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Optimal crystal growth conditions of thin films of Bi2Te3, Sb2Te3 semiconductors and their alloys BixSb2-xTe3. Applications to the thermal sensors

We have grown stoichiometrically thin films of the narrow band-gap semiconductor Bi2Te3 by molecular beam epitaxy in an ultra-high vacuum on single-crystal substrate Sb2Te3 prepared by Bridgman technique. The quality of deposited layers is controlled by X-ray diffraction, scanning electron microscope (SEM), secondary ion mass spectroscopy (SIMS) depth profiling and energy dispersive X-ray (EDX) microanalyser. It is observed that the stoichiometry of the deposited layers depended on substrate temperature and flux ratio. In addition all the deposited layers are single-crystal in the orientation of their substrates with a small shift due to the stress in layer. We have also studied the optimal growth conditions of Bi2Te3(n) and Sb2Te3(p) layers onto amorphous substrates and the thermoelectric properties of BixSb2..xTe3 alloys as a function of the bismuth concentration x. The optimal value of S (thermoelectrical power) is obtained at x=0.1. The improvement of S in comparison with that of Sb2Te3 results in the reduction in antisite defects or carrier compensation. Thermopile and pressure sensors based on Bi°. Sb1.9Te3 (p)- Bi2Te3 (n)] are constructed. These [p-n] active junctions constitute the sensitive elements of both the thermopiles and the vacuum gauges. In comparison with the (Bi-Sb) couple, an improvement in the sensitivity by factor 2.8 is achieved. Thermal simulation based on COSMOS/M software confirmed the experimental findingsWe have grown stoichiometrically thin films of the narrow band-gap semiconductor Bi2Te3 by molecular beam epitaxy in an ultra-high vacuum on single-crystal substrate Sb2Te3 prepared by Bridgman technique. The quality of deposited layers is controlled by X-ray diffraction, scanning electron microscope (SEM), secondary ion mass spectroscopy (SIMS) depth profiling and energy dispersive X-ray (EDX) microanalyser. It is observed that the stoichiometry of the deposited layers depended on substrate temperature and flux ratio. In addition all the deposited layers are single-crystal in the orientation of their substrates with a small shift due to the stress in layer. We have also studied the optimal growth conditions of Bi2Te3(n) and Sb2Te3(p) layers onto amorphous substrates and the thermoelectric properties of BixSb2..xTe3 alloys as a function of the bismuth concentration x. The optimal value of S (thermoelectrical power) is obtained at x=0.1. The improvement of S in comparison with that of Sb2Te3 results in the reduction in antisite defects or carrier compensation. Thermopile and pressure sensors based on Bi°. Sb1.9Te3 (p)- Bi2Te3 (n)] are constructed. These [p-n] active junctions constitute the sensitive elements of both the thermopiles and the vacuum gauges. In comparison with the (Bi-Sb) couple, an improvement in the sensitivity by factor 2.8 is achieved. Thermal simulation based on COSMOS/M software confirmed the experimental findings

Growth and characterization of Sb2Te3 thin films prepared by MOCVD technique in horizontal reactor

In this paper the electrical and thermoelectrical performances of p-type Sb2Te3, elaborated by metal organic chemical vapour deposition (MOCVD) in horizontal quartz reactor on pyrex glass substrate arc discussed. The quality of the deposited layers is controlled by X-ray diffraction, Scanning Elecrtron Microscope (SEM), Energy dispersive X-ray spectroscopy (EDX), and Hall effect. The deposition optimal conditions are: substrate temperature equal to 450°C, the pressure ratio R= VI/V is varied from 1 to 13 and TESb partial pressure is about 1 x] 0.4 atm. It is found that the electrical properties of Sb2Te3, change remarkably with VI/V ratio and exhibited a polyerystalline structure. The measurement of the Seebeck coefficient (115µV/K) and the mobility (196cm2/V.s) leads us to confirm the significant potential of the OMCVD method to obtain a good material promising for thermoelectric applications.In this paper the electrical and thermoelectrical performances of p-type Sb2Te3, elaborated by metal organic chemical vapour deposition (MOCVD) in horizontal quartz reactor on pyrex glass substrate arc discussed. The quality of the deposited layers is controlled by X-ray diffraction, Scanning Elecrtron Microscope (SEM), Energy dispersive X-ray spectroscopy (EDX), and Hall effect. The deposition optimal conditions are: substrate temperature equal to 450°C, the pressure ratio R= VI/V is varied from 1 to 13 and TESb partial pressure is about 1 x] 0.4 atm. It is found that the electrical properties of Sb2Te3, change remarkably with VI/V ratio and exhibited a polyerystalline structure. The measurement of the Seebeck coefficient (115µV/K) and the mobility (196cm2/V.s) leads us to confirm the significant potential of the OMCVD method to obtain a good material promising for thermoelectric applications

Synthesis and characteristics of Mg doped ZnO thin films: Experimental and ab-initio study

Structural and physical properties of Mg doped zinc oxide (MZO) thin films have been investigated. The samples have been synthesized using a simple spray pyrolysis technique. The hexagonal Wurtzite structured ZnO thin films were confirmed by X-ray diffraction (XRD). The morphology of the thin films was characterized by atomic force microscopy (AFM). The optical properties were studied in details by using ultraviolet–visible (UV–Vis) spectrophotometry and Hall Effect measurements for electrical characteristic. The results detected by AFM indicate in a qualitative and quantitative manner how the surface properties (topography, roughness) vary with Mg concentration. The optical characterization showed that the transmittance of MZO thin films increased from 75 to about 90% and optical band gap energy from 3.20 to 3.43 (eV). The electrical properties study showed the lowest resistivity value was 3.45 × 10−2 (Ω·cm), which was obtained for the film doped with ZnO:Mg (2 at.%). In order to confirm our results on optical properties, the band structure of Wurtzite Zn1−xMgxO was calculated by ab initio calculations using the Korringa–Kohn–Rostoker (KKR) method combined with the coherent potential approximation (CPA). Keywords: ZnO, Thin films, Spray pyrolysis, Optical properties, Ab-initio calculation

Imaging by Atomic Force Microscopy of the properties difference of the layers covering the facets created during SIMS analysis

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Effect of antimony concentration on the electrical and thermoelectrical properties of (Bi1−xSbx)2Te3 thin films grown by metal organic chemical vapour deposition (MOCVD) technique

International audienc

Growth of (Bil−xSbx)2Te3 thin films by metal-organic chemical vapour deposition

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