Band gap energy determination by photoacoustic spectroscopy under continuous light excitation

Astrath, N. G. C.; Sato, Francielle; Pedrochi, F.; Medina, A. N.; Bento, A. C.; Baesso, Mauro Luciano; Persson, Clas; Silva, A. Ferreira da

doi:10.1063/1.2402239

Cited by 19 publications

(13 citation statements)

References 23 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…(eV)Cryst. StructureMoS 2 1.370.121.870.040.501.251.19~1.3 * 1.87 34 2H polytypeMoSe 2 1.250.141.560.00.311.111.01~1.1 ** 1.56 34 MoTe 2 0.890.061.060.0270.170.830.80~0.8 * 1.15 25*** HfS 2 1.390.262.090.1310.701.031.001.96 44 NA1T polytypeHfSe 2 1.210.131.490.3800.281.080.961.19 44 NAWS 2 1.570.152.050.0270.481.421.30~1.3 ** 2.05 33 2H polytypeWSe 2 1.330.091.650.0200.321.241.16~1.3 ** 1.70 33 ReS 2 1.370.111.550.0490.181.261.201.52 36** 1.554 36** 3R polytypeReSe 2 1.180.061.310.0580.031.121.061.36 36** 1.387 36** SnS 2 2.360.23NANANA2.132.00~2.2 ** NA2H polytypeSnSe 2 1.240.10NANANA1.141.06NANAGaS2.870.372.920.3900.052.50<...>…”

Section: Resultsmentioning

confidence: 99%

See 1 more Smart Citation

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

Zelewski

Kudrawiec

2017

Sci Rep

View full text Add to dashboard Cite

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 ...

show abstract

Section: Resultsmentioning

confidence: 99%

“…PA spectroscopy can be used to determine the band gap as shown in refs 31,34,37 as well as the impurity and defect-related absorption 33,35 . Moreover, this technique can be used to study the surface and bulk nonradiative recombination 32 and the thermal diffusivity 36 .…”

Section: Introductionmentioning

confidence: 99%

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

Zelewski

Kudrawiec

2017

Sci Rep

View full text Add to dashboard Cite

show abstract

“…7 In this letter, we analyze the PA-signal behavior of a nanostructured WO 3 film under continuous laser excitation, using an experimental procedure similar to that described in Ref. 12. The influence of the continuous excitation in the mechanisms responsible for the generation of the PA signal is discussed and adopted to determine the band-gap energy directly from the experimental optical absorption spectra.…”

mentioning

confidence: 99%

“…Additional details of experimental conditions are described in Ref. 12. The measurements were carried out in the following way: initially, the PA spectra were taken while the sample was excited only by the modulated light.…”

mentioning

confidence: 99%

Optical band-gap determination of nanostructured WO3 film

González‐Borrero

Sato

Medina

et al. 2010

Applied Physics Letters

Self Cite

320

147

View full text Add to dashboard Cite

The optical band-gap energy of a nanostructured tungsten trioxide film is determined using the photoacoustic spectroscopy method under continuous light excitation. The mechanism of the photoacoustic signal generation is discussed. The band-gap energy is also computed by other methods. The absorption coefficient as well as the band-gap energy of three different crystal structures of tungsten trioxide is calculated by a first-principles Green's function approach using the projector augmented wave method. The theoretical study indicates that the cubic crystal structure shows good agreement with the experimental data. © 2010 American Institute of Physics. ͓doi:10.1063/1.3313945͔Tungsten trioxide ͑WO 3 ͒ films have attracted much interest during the last decade due to their potential applications. Nanostructured WO 3 films have been used in eletrochromic ͑EC͒ devices such as displays and smart windows.1-3 For this reason, a detailed understanding of the optical processes responsible for the EC effect would greatly facilitate the optimization of EC devices.4 WO 3 is a wideband-gap semiconductor. Its band-gap energy has been mainly measured by optical absorption, varying from about 2.6 to 3.0 eV. 2,5 The band gap of WO 3 is certainly of interest for both applied and fundamental aspects. The literature is however somewhat confusing. Values below 3.0 eV have mostly been obtained assuming an indirect band gap.Taking into account that the understanding of the optical processes responsible for the EC effect is an important parameter in design and optimization of EC devices, and that the band gap energy is one of the most important parameter of semiconductors, we investigate the optical absorption in the region of the fundamental band edge by the photoacoustic spectroscopy ͑PAS͒ technique. PAS has been extensively used as a nondestructive method for measuring the optical properties of semiconductors and many other materials. 6-10The nonradiative relaxation processes-which are associated with the band structure, defect-related energy loss mechanism, etc.-can be directly and very accurately obtained from the analysis of the PAS spectra. 10The optical band-gap energy ͑E g ͒ has been determined by the PAS technique using mainly two methods. In the first, the E g value is adopted as the absorption edge obtained from a linear fitting in the plot of the square of the product between the absorption coefficient and the photon energy versus the photon energy for direct band gap, or the plot of the square root of the product between the absorption coefficient and the photon energy versus the photon energy for indirect band gap. 11 In the second, E g is estimated by the changing of the derivative near the fundamental absorption edge. 7In this letter, we analyze the PA-signal behavior of a nanostructured WO 3 film under continuous laser excitation, using an experimental procedure similar to that described in Ref. 12. The influence of the continuous excitation in the mechanisms responsible for the generation of the PA signal is discussed ...

show abstract

“…A espectroscopia fotoacústica é usada extensivamente para determinar as propriedades ópticas dos materiais semicondutores pelo processo de transferência de energia que resulta na geração de calor. Recentemente foi proposto, através da EFA sobre condições contínuas de laser de excitação, uma maneira de fazer medidas diretas do valor de gap de energia dos semicondutores [47] . Geralmente o valor do gap de energia, para um semicondutor de gap direto, é assumido como o ponto inicial da absorção obtido a partir da curva do quadrado do coeficiente de absorção versus a energia do fóton (α 2 versus hν, como realizado para os filmes de PbI 2 ) ou usando o ponto inicial de absorção da curva do quadrado do coeficiente de absorção vezes a energia versus a energia, [(α hν) 2 versus hν], para semicondutores de gap indireto [46,47] .…”

Section: Caracterização óPticaunclassified

Fabricação e caracterização de filmes finos de iodeto de chumbo e cristais de iodeto de mercúrio

Filho¹,

Marques²

View full text Add to dashboard Cite

show abstract

Band gap energy determination by photoacoustic spectroscopy under continuous light excitation

Cited by 19 publications

References 23 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

Optical band-gap determination of nanostructured WO3 film

Fabricação e caracterização de filmes finos de iodeto de chumbo e cristais de iodeto de mercúrio

Contact Info

Product

Resources

About