Optical Properties of In_2xGa_2–2xO₃ Nanowires Revealed by Photoacoustic Spectroscopy

Abstract

Group III oxides, such as In 2 O 3 and Ga 2 O 3 , have proved to be good candidates as active materials for novel electronic devices, including high-mobility transistors, gas sensors, and UV photodetectors. The ability to tune optical and electronic properties is provided by alloying In 2x Ga 2−2x O 3 (InGaO) in a broad compositional range. Further development of InGaO compounds in the form of nanowires (NWs) would overcome the technological limitations, such as the substrate crystal lattice mismatch and the inability to fabricate high quality structures above the critical thickness. In this work, optical properties of alloyed InGaO NWs in a wide compositional range are carefully assessed. Unlike classical optical characterization methods, photoacoustic spectroscopy reveals the fundamental absorption edge despite the strong light scattering in porous and randomly oriented nanowires structure. An unusual compositional band gap dependence is also observed, giving insight into the phase segregation effect and increased quality of mixed NWs. In addition, photoacoustic measurements disclose potential applications of InGaO NWs in remote, light-driven loudspeakers because of intense photoacoustic effect in nanowire ensembles in this material system.

Optical markers of magnetic phase transition in CrSBr

“…More details about the principles of PAS can be found in ref. [13][14][15] The bulk CrSBr crystal for this study was grown by chemical vapour transport by direct reaction of pure Cr, Br, and S elements in a quartz ampoule. Details of the material synthesis and structural characterisation of CrSBr can be found in ESI † and ref.…”

Exponential optical absorption edge in PbS quantum dot-ligand systems on single crystal rutile-TiO2 revealed by photoacoustic and absorbance spectroscopies

“…According to the Rosencwaig-Gersho (R-G) theory [40] in which the PA intensity is proportional to the product of optical absorption coefficient and probability for heat generation, it has been assumed that the probability for heat generation by nonradiative processes is 100% [40]. Therefore, PA spectra should be in agreement with Abs spectra; thus, PA spectroscopy has been applied as a complementary technique for the optical absorption properties of opaque and light scattering materials [46,47]. However, there is a report that indicates the discrepancies between PA and Abs spectra [48].…”

InGaO3 Nanowire Networks for Deep Ultraviolet Photodetectors

“…In fact, the high concentration of Ga element will weaken the adsorption of O 2 on the surface of the NWs, resulting in a decrease in the recombination efficiency of the hole and O 2 – , thus greatly reducing the response speed and recovery speed of the photodetector . In addition, the crystal defects generated during the doping process will trap carrier, inhibit the recombination and separation speed, and reduce the optical responsiveness and response recovery speed Figure d shows the I – V characteristic curves under different intensities of light.…”

“…In this experiment, the power density of the incident UV light is 16.56 μW/cm 2 , and the effective illumination area is 0.16 cm 2 . In addition, the external quantum efficiency (EQE) and the detectability are two important parameters to appraise the performance of a photodetector, which is given by the following definition ,, normalE normalQ normalE = h c R e λ D * = R S 1 / 2 false( 2 e I normald false) 1 / 2 where R is the responsivity, h is Planck’s constant, λ is the illumination wavelength (254 nm), e is the electronic charge (1.6 × 10 –19 C), c is the velocity of light, and S is the effective area of the detector. As given in Figure f, under 1 V bias, the corresponding photocurrent gradually decreases from 1.7 to 6.5 μA with the increase of light intensity.…”

“…54 In addition, the crystal defects generated during the doping process will trap carrier, inhibit the recombination and separation speed, and reduce the optical responsiveness and response recovery speed. 55 Figure 5d shows the I−V characteristic curves under different intensities of light. The test voltage range is 0−5 V, and the photocurrent decreases gradually with the decrease of the power of the light source.…”