| SM ISO690:2012|
SPRÎNCEANU, Veaceslav; CARAMAN, Iuliana; UNTILA, Dumitru; VATAVU-CUCULESCU, Elmira; EVTODIEV, Igor; TIGHINEANU, Ion. Thermal analysis of the composition of gallium and sulfur oxides obtained by thermal oxidation of gallium (III) sulfide. In: Central and Eastern European Conferenceon Thermal Analysis and Calorimetry. Editia 4, 28-31 august 2017, Chişinău. Germany: Academica Greifswald, 2017, p. 312. ISBN 978-3-940237-47-7.
|Central and Eastern European Conference
Editia 4, 2017
Conferința "Central and Eastern European Conference" |
4, Chişinău, Moldova, 28-31 august 2017
Oxides of both Ga and In elements (Ga2O3, In2O3) are wide bandgap materials and have molecular gas adsorption properties, such as CO and CO2. They are materials with semiconductor properties, which doping with chemical elements changes the type of major charge carriers and also the characteristic properties. By thermal annealing of both Ga and In chalcogenides (Ga2S3, GaSe, Ga2Se3, In2S3, In2Se3, InSe) in a wide temperature range under normal atmospheres, their dissociation occurs with formation of Ga, In, Se, and S oxides. Both semiconductor and adsorbing properties of the synthesized oxides depends on their structure and composition. In this work, we study the influence of technological oxidation regime, in normal atmosphere, of Ga2S3 singlecrystals with own structural defects on the oxides composition, optical and photoelectric properties, as well as the adsorption of the gases formed as a result of liquid fuel (gasoline) combustion. Ga2S3 singlecrystals have been grown by chemical vapour transport (I2) of the material synthetized from Ga (5N) and S (5N) elements. Thermal annealing was carried out in normal atmosphere for 1-24 hours, at temperatures from 770K up to 1230K. Chemical composition of the materials obtained as a result of thermal annealing was analyzed by the XRD method and IR spectroscopy. Impurity state of the synthesized oxides was analyzed by absorption spectra in the fundamental edge region and photoluminescence (PL) at low temperatures. At low annealing temperatures (770K) the surface of Ga2S3 singlecrystals is covered with a micro-granular layer of Gax(SeO4)y, Ga2O3 and sulfur oxides. The composite enrichment with Ga2O3 oxide occurs at annealing temperature increase. So at high temperatures (1170-1230K) the XRD patterns contain only reflections from the Ga2O3 atomic planes. The composition of the oxides obtained at different temperatures was also determined from the analysis of the IR reflection bands. The bandgap of the Ga2O3 oxide layer, obtained by thermal annealing of Ga2S3 crystals at 770K, was determined from the absorption spectrum and represents 4.8 eV. It increases slowly at thermal annealing temperature increase. The semiconductor properties of the Ga2O3 layer depend on the energy diagram of the levels in the bandgap. Both impurity-induced levels type and energy were determined from the absorption and PL spectra. Kinetics of CO2 molecules adsorption in the Ga2O3 layer, from the Ga2S3 singlecrystals surface, is also studied in this paper.