Effect of Pressure on Direct Optical Transitions of ?-InSe

Ulrich, C.; Olguı́n, D.; Cantarero, A.; Goñi, A. R.; Syassen, K.; Chévy, A.

doi:10.1002/1521-3951(200010)221:2<777::aid-pssb777>3.0.co;2-w

Cited by 30 publications

(27 citation statements)

References 50 publications

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“…It is worth noting that PL for such crystals was reported by other authors, see for example refs 52–55 , and therefore emission properties are not further discussed in this work. In addition, the MR spectrum observed for InSe is very consistent with previous photoreflectance studies of γ-InSe 56 . The bulk InSe sample studied in this work is also γ-polytype (i.e., 2H polytype according to the nomenclature used in this work) and extended studies on exfoliated layers from such crystal can be found in refs 54,55 .…”

Section: Resultssupporting

confidence: 89%

“…So far most of them (MoS 2 , MoSe 2 , WS 2 , WSe 2 , ReS 2 , and ReSe 2 ) were studied by MR (photoreflectance, electroreflectance or piezoreflectance) 12,39–41,43–46 , but none of them was studied by PA spectroscopy. In order to discuss chemical trends for the indirect and direct gap in these materials, they are grouped in a few sets of samples going from smaller to larger atoms.…”

Section: Resultsmentioning

confidence: 99%

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Photoacoustic and modulated reflectance studies of indirect and direct band gap in van der Waals crystals

Zelewski

Kudrawiec

2017

Sci Rep

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Photoacoustic (PA) and modulated reflectance (MR) spectroscopy have been applied to study the indirect and direct band gap for van der Waals (vdW) crystals: dichalcogenides (MoS 2 , MoSe 2 , MoTe 2 , HfS 2 , HfSe 2 , WS 2 , WSe 2 , ReS 2 , ReSe 2 , SnS 2 and SnSe 2 ) and monochalcogenides (GaS, GaSe, InSe, GeS, and GeSe). It is shown that the indirect band gap can be determined by PA technique while the direct band gap can be probed by MR spectroscopy which is not sensitive to indirect optical transitions. By measuring PA and MR spectra for a given compound and comparing them with each other it is easy to conclude about the band gap character in the investigated compound and the energy difference between indirect and direct band gap. In this work such measurements, comparisons, and analyses have been performed and chemical trends in variation of indirect and direct band gap with the change in atom sizes have been discussed for proper sets of vdW crystals. It is shown that both indirect and direct band gap in vdW crystals follow the well-known chemical trends in semiconductor compounds.Van der Waals (vdW) crystals are known for a long time 1-14 but in recent years some of them have gained significant interest because of unique mechanical and optical properties of samples obtained by exfoliation of bulk material to atomically thin layers [15][16][17][18][19][20][21][22][23][24][25] . Since pioneering reports on optical properties of MoS 2 layers 15,16 , it is well established that the electronic band structure of MoS 2 strongly varies with the number of layers and exhibits indirect-to-direct band gap transition with the size reduction to a single layer. Similar studies of optical properties and the electronic band structure have been performed on other van der Waals crystals such as MoSe 2 , MoTe 2 , WS 2 , and WSe 2 22-25 . Some of them were investigated quite recently as bulk materials 13,14 but interest in these materials was low due to no potential applications in semiconductor devices. At this moment the situation is different. VdW crystals are exciting because of interesting physics of two-dimensional (2D) layers and their potential applications in novel semiconductor devices [26][27][28] . Because of this even bulk van der Waals crystals are interesting to study since many of them are not explored experimentally. One method which has never been applied to study most of van der Waals crystals is photoacoustic (PA) spectroscopy. We show that this technique is an excellent tool to study the band gap in van der Waals crystals since it is sensitive to indirect gap transitions which cannot be observed in photoluminescence. In combination with modulated reflectance (MR), which is known as a state of the art absorption-like technique to study direct optical transitions 29 , it is possible to conclude about the band gap character in van der Waals crystals and the spectral separation between the indirect and direct gap. In this work we applied PA and MR to study indirect and direct gap in many van der Waals crystals ...

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Section: Resultssupporting

confidence: 89%

Section: Resultsmentioning

confidence: 99%

Photoacoustic and modulated reflectance studies of indirect and direct band gap in van der Waals crystals

Zelewski

Kudrawiec

2017

Sci Rep

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“…In 2 Se 3 films [6], for instance, form hexagonal structures consisting of a well-known layered structure (a-phase), a defect wurtzite structure (g-phase) and anisotropic structure (n-phase), which only exists without a capping layer [5]. InSe films, on the other hand, consist of In-Se layers, forming a hexagonal unit cell over three layers [3]. Due to both the complexity of these phases and the large unit cell size as described above, the quality of the InSe film strongly depends on the growth conditions, such as deposition rates and substrate temperature.…”

Section: Introductionsupporting

confidence: 87%

“…The system is particularly interesting because of the existence of several different phases, dependent upon pressure applications [3], heat treatments [4] and presence of a capping layer [5]. In 2 Se 3 films [6], for instance, form hexagonal structures consisting of a well-known layered structure (a-phase), a defect wurtzite structure (g-phase) and anisotropic structure (n-phase), which only exists without a capping layer [5].…”

Section: Introductionmentioning

confidence: 99%

Structural and electrical properties of InSe polycrystalline films and diode fabrication

Hirohata¹,

Moodera²,

Berera

2006

Thin Solid Films

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“…The spectra of the optical absorption of gallium and indium monoselenides subjected to a uniaxial pressure Р ≈ 75 kPa indicate on the absence of changes in the energy spectra of these semiconductors. It is in agreement to the data of [6,7] since, according to [6], the decrease of the energy gap E g of GaSe under pressure becomes essential only at Р ∼ 10 8 Pa. It makes possible to relate the observed variations of V oc and I sc in the applies range of pressure with changes occurring at the interface of the n-InSe-р-GaSe HJ.…”

Section: Experimental Details and Discussionmentioning

confidence: 99%

Photovoltaic Effect in the Anisotype GaSe-InSe Heterojunctions Under Pressure

2005

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The influence of mechanical pressure along the direction across the interface of n-InSe-pGaSe heterojunctions on saturation photo-e.m.f. and short-circuit current is investigated. It is shown that at the InSe/GaSe optical contacts subjected to a pressure P = 35-40 kPa an increase of the open-circuit voltage nearly twice and short-circuit current more than by a factor of five in comparison to the initial samples takes place. It makes possible to predict a possibility of considerable increasing photoconversion efficiency of such structures.

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Effect of Pressure on Direct Optical Transitions of ?-InSe

Cited by 30 publications

References 50 publications

Photoacoustic and modulated reflectance studies of indirect and direct band gap in van der Waals crystals

Photoacoustic and modulated reflectance studies of indirect and direct band gap in van der Waals crystals

Structural and electrical properties of InSe polycrystalline films and diode fabrication

Photovoltaic Effect in the Anisotype GaSe-InSe Heterojunctions Under Pressure

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