Single crystal growth and characterization of copper aluminum indium disulfide chalcopyrites

2012

AIP Advances

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Optical examination of a chaocogenide compound AgAlS2 which can spontaneously transfer to a AgAlO2 oxide has been investigated by thermoreflectance (TR) spectroscopy herein. The single crystals of AgAlS2 were grown by chemical vapor transport (CVT) method using ICl3 as a transport agent sealed in evacuated quartz tubes. The as-grown AgAlS2 crystals essentially possess a transparent and white color in vacuum. The crystal surface of AgAlS2 becomes darkened and brownish when putting AgAlS2 into atmosphere for reacting with water vapor or hydrogen gas. Undergoing the chemical reaction process, oxygen deficient AgAlO2-2x with brownish and reddish-like color on surface of AgAlS2 forms. The transition energy of deficient AgAlO2-2x was evaluated by TR experiment. The value was determined to be ∼2.452 eV at 300 K. If the sample is kept dry and moved away from moisture, AgAlS2 crystal can stop forming more deficient AgAlO2-2x surface oxides. The experimental TR spectra for the surface-reacted sample show clearly two transition features at EW=2.452 eV for deficient AgAlO2-2x and EU=3.186 eV for AgAlS2, respectively. The EU transition belongs to direct band-edge exciton of AgAlS2. Alternatively, for surface-oxidation process of AgAlS2 lasting for a long time, a AgAlO2 crystal with yellowish color will eventually form. The TR measurements show mainly a ground-state band edge exciton of E OX 1 detected for AgAlO2. The energy was determined to be E OX 1 =2.792 eV at 300 K. The valence-band electronic structure of AgAlS2 has been detailed characterized using polarized-thermoreflectance (PTR) measurements in the temperature range between 30 and 340 K. Physical chemistry behaviors of AgAlS2 and AgAlO2 have been comprehensively studied via detailed analyses of PTR and TR spectra. Based on the experimental analyses, optical and chemical behaviors of the AgAlS2 crystals under atmosphere are realized. A possible optical-detecting scheme for using AgAlS2 as a humidity sensor has also been proposed

Section: A Chemical Reactions and Compounds' Formationmentioning

confidence: 94%

“…29,31 The compounds of the crystals were prepared from the elements (Ag: purity 99.999%, Al: purity 99.9995%, and S: purity 99.999%) by reaction at 875 • C for 2 days in an evacuated quartz ampoule. To improve stoichiometry, sulfur with 1 mol% in excess was added with respect to the stoichiometric mixture of the constituent elements.…”

Section: Methodsmentioning

confidence: 99%

Surface sensing behavior and band edge properties of AgAlS2: Experimental observations in optical, chemical, and thermoreflectance spectroscopy

2012

AIP Advances

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“…Single crystals of Cu(Al x In 1-x )S 2 solid solutions with x=0, 0.2, 0.4, 0.5, 0.6, 0.7, and 1.0 were grown by CVT method [7,8] using ICl 3 as a transport agent. Cu(Al x In 1-x )S 2 compounds were prepared from the powdered mixture of elements (Cu: -purity 99.995%, Al: -purity 99.9995%, In: -purity 99.9999%, and S: -purity 99.999%) in the stoichiometric proportion by reaction at 850 °C for 3 days in evacuated quartz ampoules.…”

Section: Methodsmentioning

confidence: 99%

Structural and Band-Edge Properties of Cu(AlxIn1-X)S2 (0≤x≤1) Series Chalcopyrite Semiconductors

Cai

et al. 2012

SSP

We have demonstrated structural and electronic properties of a series solar energy crystals Cu(AlxIn1-x)S2 (0<=x<=1) by using measurement techniques of X-ray diffraction, polarized thermoreflectance (PTR), and X-ray photoelectron spectroscopy (XPS). Single crystals of Cu(AlxIn1-x)S2 (0<=x<=1) (0 and E ^ polarizations. The PTR spectra clearly showed that the energy value of D increases with the increase of Al content x in the Cu(AlxIn1-x)S2 (0<=x<=1) series due to the enhanced strain in the lattice. The composition-dependent crystal-field-splitting energies can be evaluated and determined to be D(x)= (10±2)+( 139±5)×x meV. Based on the experimental analyses, the crystal structure and valence-band structure of the Cu(AlxIn1-x)S2 (0<=x<=1) (0<=x<=1) series are thus realized.

“…Single crystals of CuAlS 2 and AgAlS 2 were grown by the CVT method using ICl 3 as a transport agent [21][22][23]. The stoichiometric compounds were prepared from the powdered elements (Cu: purity 99.999%, Ag: purity 99.9995%, Al: purity 99.9995%, and S: purity 99.999%).…”

Section: A Crystal Growthmentioning

confidence: 99%

Optical behavior and structural property of CuAlS₂ and AgAlS₂ wide-bandgap chalcopyrites

2014

Appl. Opt.

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Single crystals of CuAlS₂ and AgAlS₂ were grown by chemical vapor transport method using ICl₃ as the transport. The as-grown CuAlS₂ crystals reveal transparent and light-green color. Most of them possess a well-defined (112) surface. The AgAlS₂ crystals essentially show transparent and white color in vacuum. As the AgAlS₂ was put into the atmosphere, the crystal surface gradually darkened and became brownish because of the surface reaction with humidity or hydrogen gas. After a long-term chemical reaction process, the AgAlS₂ will transform into a AgAlO₂ oxide with yellow color. From x-ray diffraction measurements, both CuAlS₂ and AgAlS₂ as-grown crystals show single-phase and isostructural to a chalcopyrite structure. The (112) face is more preferable for the formation of the chalcopyrite crystals. The energies of interband transitions of the CuAlS₂ and AgAlS₂ were determined accurately by thermoreflectance measurements in a wide energy range of 2-6 eV. The valence-band electronic structures of CuAlS₂ and AgAlS₂ have been detailed and characterized using polarized-thermoreflectance measurements in the temperature range between 30 and 300 K. The band-edge transitions belonging to the E(∥) and E(⊥) polarizations have been, respectively, identified. The band edge of AgAlS₂ is near 3.2 eV while that of AgAlS₂ is about 3.5 eV. On the basis of the experimental analyses, optical and sensing behaviors of the chalcopyrite crystals have been realized.