Raman microscopy was used to investigate microstructural properties of amorphous MoO3 thin films that
had been subjected to a photochromic (PC) or electrochromic (EC) process. The Raman spectra changed
reversibly when the films went through PC or EC coloration and decoloration cycles. Different molybdenum
bronzes were produced with PC and EC treatments, as indicated by the shifts in the Raman bands. The same
observation was made in the surface photovoltage spectral experiments. Hence, it was concluded that the
microstructure of molybdenum bronze was affected by the coloration means (PC or EC process); the injected
cations in an EC process were bonded to the triply coordinated O atoms, whereas the injected H+ ions in a
PC process were bonded to both the triply coordinated and doubly coordinated O atoms. The size of the
injected cations via EC processes had little effect on the microstructure of the colored films.
Mobility engineering is one of the most important challenges that determine the optoelectronic performance of two-dimensional (2D) materials. So far, charged-impurity scattering and electrical-contact barriers have been suppressed through high-κ dielectrics and seamless contact engineering, giving rise to carrier-mobility improvement in exfoliated 2D semiconducting MoS2. Here we demonstrate a facile and scalable technique to effectively suppress both Coulomb scattering and electron-phonon scattering via the HfO2 overlayer, resulting in a large mobility improvement in CVD-grown monolayer MoS2, in excess of 60 cm2 V-1 s-1. Surface passivation and suppression of Coulomb scattering can partially contribute to the mobility increase. Interestingly, we correlate the mobility increase with phonon quenching through Raman and temperature-dependent mobility measurements. The experimental method is facile, industrially scalable, and renders phonon engineering an additional leverage towards further improvements in 2D semiconductor mobility and device performance.
Zinc oxide (ZnO) materials irradiated with 350 MeV 56Fe21+ ions were studied by Raman spectroscopy, Photoluminescence spectra (PL) and Transmission electron microscope (TEM). After 56Fe21+ ion irradiation, a strong oxygen vacancy (Vo) related defect absorption peak at 576 cm−1 and an interstitial zinc (Zni) -related defect at 80 cm−1~200 cm−1 formed, and with the increase of dose, the absorption peak was obviously enhanced. Through theoretical calculation, different Raman incident light test methods wereused to determine the oxygen vacancy defect (Vo). There were no significant variation tendencies in the other Raman characteristic lines. Our results demonstrate an energy loss process contributing to the defect structure during irradiation. TEM images showed a lot of fundamental defects. But we see no distinct amorphization in the samples in the electron diffraction images, indicating that the higher energy and irradiation dose hardly affected the structure and performance of zinc oxide.
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