A continuously tunable long-wavelength cw IR source for high-resolution spectroscopy and trace-gas detection

Eckhoff, W. C.; Putnam, Roger S.; Wang, Shunxi; Curl, R. F.; Tittel, Frank K.

doi:10.1007/bf01828938

Cited by 36 publications

(7 citation statements)

References 23 publications

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“…These materials are wide bandgap semiconductors and are of interest for a range of applications from electrochemistry to optoelectronics, − gas sensing, and nonlinear optics . Over the last 30 years, a number of papers have studied the properties of such layered crystals with common examples being GaSe, InTe, and the related compound In 2 Se 3 . − However, work on exfoliation has only started recently with a number of papers reporting production of few-layer InSe and GaSe by mechanical cleavage or chemical exfoliation as well as vapor phase growth of thin layers. ,− Such studies have found these exfoliated materials to be of interest for applications such as photodetectors and in nonlinear optics. ,− …”

Section: Introductionmentioning

confidence: 99%

Preparation of Gallium Sulfide Nanosheets by Liquid Exfoliation and Their Application As Hydrogen Evolution Catalysts

et al. 2015

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Here we demonstrate the production of large quantities of gallium sulfide (GaS) nanosheets by liquid exfoliation of layered GaS powder. The exfoliation was achieved by sonication of the powder in suitable solvents. The variation of dispersed concentration with solvent was consistent with classical solution thermodynamics and showed successful solvents to be those with Hildebrand solubility parameters close to 21.5 MPa 1/2 . In this way, nanosheets could be produced at concentrations of up to ~0.2 mg/ml with lateral sizes and thicknesses of 50-1000 nm and 3-80 layers, respectively. The nanosheets appeared to be relatively defect free although oxygen was observed in the vicinity of the edges. Using controlled centrifugation techniques, it was possible to prepare dispersions containing size-selected nanosheets.Spectroscopic measurements showed the optical properties of the dispersions to vary strongly with nanosheet size, allowing the elucidation of spectroscopic metrics for in-situ estimation of nanosheet size and thickness. These techniques allow the production of nanosheets with controlled sizes which will be important for certain applications. To demonstrate this, we prepared films of GaS nanosheets of three different sizes for use as hydrogen evolution electrocatalysts. We found a clear correlation between performance and size showing small nanosheets to be more effective. This is consistent with the catalytically active sites residing on the nanosheet edges.

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Section: Introductionmentioning

confidence: 99%

Preparation of Gallium Sulfide Nanosheets by Liquid Exfoliation and Their Application As Hydrogen Evolution Catalysts

et al. 2015

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“…The family of III-VI semiconductors, such as GaS, GaSe, GaTe and InSe has been extensively studied due to their nonlinear optical properties [1] and their possible application in optical devices [2,3]. They crystallize in a layered structure, each layer being composed of four monoatomic anion-cation-cation-anion layers.…”

Section: Introductionmentioning

confidence: 99%

Theoretical studies of defect states in GaTe

Rak

Mahanti

Mandal

et al. 2008

J. Phys.: Condens. Matter

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Using first principle electronic structure calculations within density functional theory and the supercell model, we have investigated the nature and formation energies of defect states associated with Ga and Te vacancies and Ge and Sn substitutional impurities in GaTe. We have also calculated the band structure of pure GaTe for comparison with systems with defects and also to find out the importance of spin-orbit interaction (SOI) on its band structure. We find that the top valence band at the Γ-point shifts up in energy by ∼0.1 eV due to the mixing of Te p(x)-p(y) and p(z) bands, this splitting being considerably smaller than in atoms where it is ∼0.8 eV. From an analysis of charge densities and band structures associated with the defect states, we find that most of them are strongly localized and lie deep in the band gap region. The calculated binding energy of the deep defect state and the ε(-1/-2) transition level associated with the Ga vacancy appears to be in good agreement with experiment. Formation energy calculations suggest that V(Ga) is the preferred intrinsic defect in GaTe.

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“…The layered materials of the III-VI family like gallium telluride or gallium selenide are of special interest for its potential applications in nonlinear and optical bistable devices. 1,2 GaTe is a direct-gap semiconductor [3][4][5][6] with strong excitonic absorption at room temperature ͑RT͒. GaTe belongs to the space group 7 B2/m, which has a monoclinic unit cell.…”

Section: Introductionmentioning

confidence: 99%

Optical absorption in GaTe under high pressure

Pellicer‐Porres¹,

Manjón²,

Segura³

et al. 1999

Phys. Rev. B

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This paper reports on the pressure dependence at room temperature of the absorption coefficient of the layered semiconductor gallium telluride. The absorption edge in the explored pressure range ͑up to 6.1 GPa͒ can be accounted for through the superposition and interaction of a direct gap and an indirect gap. The pressure shift of the direct gap is strongly nonlinear, starting at low pressure with a coefficient of Ϫ85.7 Ϯ0.4 meV/GPa and exhibiting a minimum at around 2.9 GPa. The exciton binding energy decreases under pressure, which can be related to the increase of the dielectric constant. The broadening of the exciton line is explained through phonon-assisted intervalley scattering of conduction-band electrons after the crossover between direct and indirect gaps, with an estimation of the related intervalley deformation potential. ͓S0163-1829͑99͒16035-1͔

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A continuously tunable long-wavelength cw IR source for high-resolution spectroscopy and trace-gas detection

Cited by 36 publications

References 23 publications

Preparation of Gallium Sulfide Nanosheets by Liquid Exfoliation and Their Application As Hydrogen Evolution Catalysts

Preparation of Gallium Sulfide Nanosheets by Liquid Exfoliation and Their Application As Hydrogen Evolution Catalysts

Theoretical studies of defect states in GaTe

Optical absorption in GaTe under high pressure

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