Characterization of Optical and Photoelectrical Properties of ZnO Crystals

We characterized optical and photoelectrical properties of undoped and Ga-doped ZnO layers differently grown on sapphire substrates by using complementary optical methods. Different stimulated emission threshold values for ZnO epitaxial layers grown by pulsed laser deposition and MBE methods were attributed to crystalline quality of the layers and the growth method used. Different carrier lifetimes in various ZnO epitaxial layers are explained by defect-related and intrinsic mechanisms of recombination

Photoluminescence of CdZnTe thick films obtained by close-spaced vacuum sublimation

Polycrystalline Cd1 xZnxTe thick films with thicknesses of about 30 μm have been deposited on a Mo coated glass substrate by means of close-spaced vacuum sublimation technique. X-ray diffraction measurements have shown that the films obtained have only cubic zinc blende phase. The influence of Zn concentration on the photoluminescence (PL) spectra of Cd1 xZnxTe films was investigated. This let us determine the nature and energy structure of the intrinsic defects and residual impurities in the films.This work was supported by Grant State Fund for Fundamental Research (project NGP/F61/087) and by the Ministry of Education and Science of Ukraine (Grant no. 0110U001151) by the National Academy of Sciences of Ukraine (Grants nos. BС-157-15 and B-146-15)

Post-growth treatment of SnxSy thin films

In this study, the effect of post-growth thermal annealing and laser irradiation on phase composition, structural, optical and electrical properties of SnS2 obtained by the close-spaced sublimation on ITO substrates was studied. It was found, by using EDS, XRD and Raman methods that as-grown samples have single phase SnS2 structure and their chemical composition is close to stoichiometric

Composition dependence of structural and optical properties of Cd1−xZnxTe thick films obtained by the close-spaced sublimation

New approach for deposition of Cd1−xZnxTe thick films has been developed. Effect of chemical composition on Cd1−xZnxTe thick films properties was studied. The proposed approach allows obtaining of high-quality Cd1−xZnxTe thick films. Compositional dependence of Raman modes frequencies was established.This paper reports the results of structural, photoluminescence and Raman characterization of thick Cd1−xZnxTe films with different zinc concentration obtained by the close spaced vacuum sublimation method. The analysis of the X-rays patterns allows us to determine the effect of the zinc concentration on crystal quality of the films. It was found that samples with x ≈ 0.10 and x ≈ 0.32 have high crystal quality. However, with increasing of zinc concentration the crystal quality decreases. This result was confirmed by the photoluminescence study. Namely, the significant degradation of optical properties for the samples with high zinc concentration (x > 0.32) was observed. Raman spectroscopy reveals the relation between zinc concentration and vibrational properties of the films. Also, the micro-Raman method shows that obtained films are uniform and free of tellurium inclusions.This work was supported by Erasmus Ianus Programme and by the Ministry of Education, Science of Ukraine (Grant No. 0115U003242, 0113U000131) by theNational Academy of Sciences of Ukraine (Grants Nos. BС-157-15 and B-146-15) and State Fund for Fundamental Research (project N GP/F61/087)

Composition dependence of structural and optical properties of Cd1-xZnxTe thick films obtained by the close-spaced sublimation

У даній роботі представлені результати структурної, фотолюмінесценції та рамановської характеристики товстих плівок Cd1-xZnxTe з різною концентрацією цинку, отриманих методом вакуумної сублімаціїз близькою відстанню. Аналіз зразків рентгенівських променів дозволяє визначити вплив концентрації цинку на якість кристалів плівок. Було встановлено, що зразки з х ≈ 0,10 і х ≈ 0,32 мають високу якість кристалів. Однак зі збільшенням концентрації цинку якість кристала зменшується. Цей результат був підтверджений дослідженням фотолюмінесценції. А саме, спостерігалося значне погіршення оптичних властивостей зразків з високою концентрацією цинку (х> 0,32). Спектроскопія комбінаційного розсіювання показує співвідношення між концентрацією цинку і коливальними властивостями плівок. Крім того,метод мікрораманів показує, що отримані плівки є однорідними і вільними від включень телуру.В настоящей работе представлены результаты структурной, фотолюминесценции и рамановской характеристики толстых пленок Cd1-xZnxTe с различной концентрацией цинка, полученных методом вакуумной сублимации с близким расстоянием. Анализ рентгенограмм позволяет определить влияние концентрации цинка на качество кристаллов пленок. Было обнаружено, что образцы с x ≈ 0,10 и x ≈ 0,32 имеют высокое качество кристалла. Однако с увеличением концентрации цинка качество кристаллов уменьшается. Этот результат был подтвержден исследованием фотолюминесценции. А именно, наблюдалось значительное ухудшение оптических свойств для образцов с высокой концентрацией цинка (х> 0,32). Рамановская спектроскопия выявляет связь между концентрацией цинка и колебательными свойствами пленок. Кроме того, метод микрораманов показал, что полученные пленки являются однородными и не содержат включений теллура.This paper reports the results of structural, photoluminescence and Raman characterization of thick Cd1−xZnxTe films with different zinc concentration obtained by the close spaced vacuum sublimation method. The analysis of the X-rays patterns allows us to determine the effect of the zinc concentration on crystal quality of the films. It was found that samples with x ≈ 0.10 and x ≈ 0.32 have high crystal quality. However, with increasing of zinc concentration the crystal quality decreases. This result was confirmed by the photoluminescence study. Namely, the significant degradation of optical properties for the samples with high zinc concentration (x > 0.32) was observed. Raman spectroscopy reveals the relation between zinc concentration and vibrational properties of the films. Also, the micro-Raman method shows that obtained films are uniform and free of tellurium inclusions.This work was supported by Erasmus Ianus Programme and by the Ministry of Education, Science of Ukraine (Grant No. 0115U003242, 0113U000131) by the National Academy of Sciences of Ukraine (Grants Nos. BС-157-15 and B-146-15) and State Fund for Fundamental Research (project N GP/F61/087)

Composition dependence of structural and optical properties of Cd1-xZnxTe thick films obtained by the close-spaced sublimation

У даній роботі представлені результати структурної, фотолюмінесценції та рамановської характеристики товстих плівок Cd1-xZnxTe з різною концентрацією цинку, отриманих методом вакуумної сублімаціїз близькою відстанню. Аналіз зразків рентгенівських променів дозволяє визначити вплив концентрації цинку на якість кристалів плівок. Було встановлено, що зразки з х ≈ 0,10 і х ≈ 0,32 мають високу якість кристалів. Однак зі збільшенням концентрації цинку якість кристала зменшується. Цей результат був підтверджений дослідженням фотолюмінесценції. А саме, спостерігалося значне погіршення оптичних властивостей зразків з високою концентрацією цинку (х> 0,32). Спектроскопія комбінаційного розсіювання показує співвідношення між концентрацією цинку і коливальними властивостями плівок. Крім того,метод мікрораманів показує, що отримані плівки є однорідними і вільними від включень телуру.В настоящей работе представлены результаты структурной, фотолюминесценции и рамановской характеристики толстых пленок Cd1-xZnxTe с различной концентрацией цинка, полученных методом вакуумной сублимации с близким расстоянием. Анализ рентгенограмм позволяет определить влияние концентрации цинка на качество кристаллов пленок. Было обнаружено, что образцы с x ≈ 0,10 и x ≈ 0,32 имеют высокое качество кристалла. Однако с увеличением концентрации цинка качество кристаллов уменьшается. Этот результат был подтвержден исследованием фотолюминесценции. А именно, наблюдалось значительное ухудшение оптических свойств для образцов с высокой концентрацией цинка (х> 0,32). Рамановская спектроскопия выявляет связь между концентрацией цинка и колебательными свойствами пленок. Кроме того, метод микрораманов показал, что полученные пленки являются однородными и не содержат включений теллура.This paper reports the results of structural, photoluminescence and Raman characterization of thick Cd1−xZnxTe films with different zinc concentration obtained by the close spaced vacuum sublimation method. The analysis of the X-rays patterns allows us to determine the effect of the zinc concentration on crystal quality of the films. It was found that samples with x ≈ 0.10 and x ≈ 0.32 have high crystal quality. However, with increasing of zinc concentration the crystal quality decreases. This result was confirmed by the photoluminescence study. Namely, the significant degradation of optical properties for the samples with high zinc concentration (x > 0.32) was observed. Raman spectroscopy reveals the relation between zinc concentration and vibrational properties of the films. Also, the micro-Raman method shows that obtained films are uniform and free of tellurium inclusions.This work was supported by Erasmus Ianus Programme and by the Ministry of Education, Science of Ukraine (Grant No. 0115U003242, 0113U000131) by the National Academy of Sciences of Ukraine (Grants Nos. BС-157-15 and B-146-15) and State Fund for Fundamental Research (project N GP/F61/087)

Investigating the Superconducting Properties and Surface Morphology of Sputtered Nb Films on Cu Due to Laser Treatment

Bulk niobium is currently the material of choice for superconducting radio frequency (SRF) cavities and is a well matured process. However, it is possible that SRF cavities could be further improved beyond bulk Nb by sputtering thin Nb films onto Cu cavities. Copper has a greater thermal conductivity than Nb and is also easier to machine, while sputtering films on the surface reduces the amount of Nb used to fabricate the whole cavity. However, sputtering Nb on Cu produces other issues, for example, the surface quality of the Cu affects the quality of the Nb deposited on the surface and therefore the superconducting parameters. As the Nb on the surface is not perfect, the magnetic field produced by the RF can enter the cavity earlier than expected, producing RF losses, which can in turn lead to a quench. One approach is to treat the Nb post deposition by irradiating the surface using a laser to polish the surface of the Nb and increase the surface magnetic field that the cavity can maintain while remaining in the Meissner state. A magnetic field penetration experiment designed and built at Daresbury Laboratory has been used to measure the field of full flux penetration to characterize the effect of the laser treatment on the superconducting properties of the Nb. Surface characterization and the response of the Nb in a dc magnetic field have also been performed to try and provide an explanation for the change in the superconducting properties. The results demonstrate that the laser treatment can lead to an increase in the magnetic field at which the flux penetrates from one side of the sample to the other, thus it could potentially improve the performance of Nb coated RF cavities

Quality improvement of CZTS thin films deposited by spray pyrolysis method using pulsed Nd: YAG laser irradiation

In this work, thin films of Cu2ZnSnS4 (CZTS) were grown by spray-pyrolysis method and were irradiated by pulsed Nd: YAG laser. Their morphological, chemical, structural and substructural characteristics were investigated using AFM, SEM, EDS, XRD and Raman spectroscopy. Upon laser irradiation, improvement of crystallinity, stoichiometry and surface morphology were observed in the obtained CZTS thin films with the normal distribution of newly-formed particles throughout the plane. It was shown that the laser processing by pulsed Nd: YAG laser is an alternative method to the traditional post-growth thermal annealing and can be used not only for local annealing but also for annealing in various depths in the films

Photoluminescence of CdZnTe thick films obtained by close-spaced vacuum sublimation

Polycrystalline Cd1 xZnxTe thick films with thicknesses of about 30 μm have been deposited on a Mo coated glass substrate by means of close-spaced vacuum sublimation technique. X-ray diffraction measurements have shown that the films obtained have only cubic zinc blende phase. The influence of Zn concentration on the photoluminescence (PL) spectra of Cd1 xZnxTe films was investigated. This let us determine the nature and energy structure of the intrinsic defects and residual impurities in the films.This work was supported by Grant State Fund for Fundamental Research (project NGP/F61/087) and by the Ministry of Education and Science of Ukraine (Grant no. 0110U001151) by the National Academy of Sciences of Ukraine (Grants nos. BС-157-15 and B-146-15)

Post-growth treatment of SnxSy thin films

In this study, the effect of post-growth thermal annealing and laser irradiation on phase composition, structural, optical and electrical properties of SnS2 obtained by the close-spaced sublimation on ITO substrates was studied. It was found, by using EDS, XRD and Raman methods that as-grown samples have single phase SnS2 structure and their chemical composition is close to stoichiometric