Time evolution studies of laser induced chemical changes in InAs nanowire using Raman spectroscopy

Abstract

We report the study of time evolution of chemical changes on the surface of an InAs nanowire (NW) on laser irradiation in different power density regime, using Raman spectroscopy for a time span of 8–16 min. Mixture of metastable oxides like InAsO4, As2O3 are formed upon oxidation, which are reflected as sharp Raman peaks at ∼240–254 and 180–200 cm−1. Evidence of removal of arsenic layer by layer is also observed at higher power density. Position controlled laser induced chemical modification on a nanometer scale, without changing the core of the NW, can be useful for NW based device fabrication.

Morphology and composition of oxidized InAs nanowires studied by combined Raman spectroscopy and transmission electron microscopy

“…The oxidation process consists of several parallel reaction schemes, where each scheme typically includes two sequential reactions [19,28]. Let us first consider the oxidation reaction kinetics of InAs surfaces in general terms, valid for all possible reactions including InAs.…”

“…To this end, locally accelerating the reaction by focused laser irradiation has been demonstrated and can be combined with micro-Raman spectroscopy to provide information about the vibrational modes of individual semiconductor nanowires [8][9][10][11] and also conveying information about the elemental composition [12,13], crystal properties [14], and defects [15] as well as free carrier densities and mobilities [16]. Also, at high intensities, focused laser irradiation has been shown to enable controlled local cutting or chemical modification of InAs and GaAs nanowires by local oxidation and formation of crystalline arsenic [17][18][19][20][21] and enables welding of metal nanowires [22]. This opens the possibility for using focused laser beams for simultaneous micro-Raman characterization and engineering new functionality into nanowire devices.…”

Spatially resolved Raman spectroscopy study of uniform and tapered InAs micro‐nano wires: correlation of strain and polytypism

“…[25] Therein, we show that blue shift and reduction in FWHM at higher powers (6 mW), whereas, larger redshift and increase in FWHM are expected, if it was due to heating. [25] Further, for~0.3 mW, no change was observed over time evolution of 8 min. The effect of confinement is also rejected because the diameters we are studying that are much beyond phonon confinement effects are expected to occur (<200 nm).…”

“…Raman spectroscopy is especially useful for study of MNWs, as density of MNWs is low, and it is difficult to study them using more conventional techniques, like X-ray diffraction. In our earlier study of laser power-dependent time evolution of Raman spectra of InAs MNW (diameter (d)~1 μm), a TO like mode~214 cm À1 [25] was noted, whereas, for bulk InAs, TO phonon wavenumber is 217.5 cm À1 . [26] In the present study, we have investigated this observed red shift in InAs MNW, using spatially resolved Raman spectroscopy (SRRS) on several MNWs of a different kind.…”

Raman spectroscopy and electrical properties of InAs nanowires with local oxidation enabled by substrate micro-trenches and laser irradiation

“…An alternative approach which has recently emerged is the possibility of using a high intensity focused laser beam to locally induce chemical changes in the NW 14 . By combination of Raman spectroscopy 15 and transmission electron microscopy 16 it has been established that for the case of InAs the high intensity laser, in the presence of ambient air conditions, promotes the oxidation process As 2 O 3 +2InAs→In 2 O 3 +4As which converts the irradiated parts of the NW surface to crystalline arsenic and polycrystalline indium oxide 16 . However, so far, only little is known about the properties of the resulting structures and the spatial resolution that can be achieved has not been analyzed.…”