One-dimensional pure zinc oxide (ZnO) and Y-doped ZnO nanorod arrays have been successfully fabricated on the silicon substrate for comparison by a simple hydrothermal process at the low temperature of 90°C. The Y-doped nanorods exhibit the same c-axis-oriented wurtzite hexagonal structure as pure ZnO nanorods. Based on the results of photoluminescence, an enhancement of defect-induced green-yellow visible emission is observed for the Y-doped ZnO nanorods. The decrease of E₂(H) mode intensity and increase of E₁(LO) mode intensity examined by the Raman spectrum also indicate the increase of defects for the Y-doped ZnO nanorods. As compared to pure ZnO nanorods, Y-doped ZnO nanorods show a remarked increase of saturation magnetization. The combination of visible photoluminescence and ferromagnetism measurement results indicates the increase of oxygen defects due to the Y doping which plays a crucial role in the optical and magnetic performances of the ZnO nanorods.

The rotational states of an adsorbed dipole molecule in an external electric field were investigated. The surface hindering potential was modeled as a finite conical well and a dipole-field interaction was added to the hindering potential. The molecular wave functions were expressed in terms of the eigenfunctions of molecular hindered rotation in the absence of electric field. Eigenenergies were determined by the matrix diagonalization procedures. Our results showed that, for both vertically and horizontally adsorbed molecules, there is avoided crossing between two adjacent rotational energy levels, as the field strength is increased, and finally all state energies decrease rapidly as the field strength is strong enough. The avoided crossing is due to the redistribution of wave function between different potential well regions. By employing the sudden unhindrance approximation, the rotational-state distributions of molecules desorbing from a solid surface in the presence of external electric field were calculated. Our results showed that the rotational-state distributions are significantly influenced by the external electric field. Since the electric field increases the ground-state energy of adsorbed molecule, the distribution shifts towards the high-$J$ region if the electric field is applied to orient the molecular axis against the molecular preferred orientation. On the contrary, the distribution shifts towards the low-$J$ region if the electric field is applied to orient the molecular axis towards molecular preferred orientation because the electric field decreases the ground-state energy of adsorbed molecule. The solutions to the finite conical well were also used to calculate the rotational alignment in the photodesorption of CO from ${\mathrm{Cr}}_2{\mathrm{O}}_3\mathrm{}\left(0001\right).$ Our results showed that at low-$J$ values the CO molecules desorb like a helicopter, while at high-$J$ values a cartwheel-like motion is preferred. This result is in qualitative agreement with the experimental observation.

In this paper, the synthesis and characterization of CuIn_1−xGa_xSe₂ (0 ≤ x ≤ 1) nanocrystals are reported with the influences of x value on the structural, morphological, and optical properties of the nanocrystals. The X-ray diffraction (XRD) results showed that the nanocrystals were of chalcopyrite structure with particle size in the range of 11.5–17.4 nm. Their lattice constants decreased with increasing Ga content. Thus, the x value of the CuIn_1−xGa_xSe₂ nanocrystals was estimated by Vegard’s law. Transmission electron microscopy (TEM) analysis revealed that the average particle size of the nanocrystals agreed with the results of XRD. Well-defined lattice fringes were shown in the TEM images. An analysis of the absorption spectra indicated that the band gap energy of these CuIn_1−xGa_xSe₂ nanocrystals was tuned from 1.11 to 1.72 eV by varying the x value from 0 to 1. The Raman spectra indicated that the A₁ optical vibrational mode of the nanocrystals gradually shifted to higher wavenumber with increasing x value. A simple theoretical equation for the A₁ mode frequency was proposed. The plot of this equation showed the same trend as the experimental data.

The SnS/SnS₂ heterostructure was fabricated by the chemical vapor deposition method. The crystal structure properties of SnS₂ and SnS were characterized by X-ray diffraction (XRD) pattern, Raman spectroscopy, and field emission scanning electron microscopy (FESEM). The frequency dependence photoconductivity explores its carrier kinetic decay process. The SnS/SnS₂ heterostructure shows that the ratio of short time constant decay process reaches 0.729 with a time constant of 4.3 × 10⁻⁴ s. The power-dependent photoresponsivity investigates the mechanism of electron–hole pair recombination. The results indicate that the photoresponsivity of the SnS/SnS₂ heterostructure has been increased to 7.31 × 10⁻³ A/W, representing a significant enhancement of approximately 7 times that of the individual films. The results show the optical response speed has been improved by using the SnS/SnS₂ heterostructure. These results indicate an application potential of the layered SnS/SnS₂ heterostructure for photodetection. This research provides valuable insights into the preparation of the heterostructure composed of SnS and SnS₂, and presents an approach for designing high-performance photodetection devices.

The 2H molybdenum telluride (MoTe₂) photodetector structures were made with inserting 1T-MoTe₂ interlayer contacts. The optical response properties such as photoconductivity (PC) spectroscopy, illumination intensity dependent photoresponsivity, frequency dependent photocurrent, and time-resolved photoresponse were carried out in this study. In PC spectra, a much higher photoresponsivity of 2H-MoTe₂ were observed by inserting 1T-MoTe₂ interlayer contact. The frequency dependent photocurrent and time-resolved photoresponse investigations explore the carrier kinetic decay process of MoTe₂ with different electrode contact. The Schottky barrier heights (SBH) extracted by thermionic emission theory were also investigated by inserting 1T-MoTe₂ interlayer contacts. The results show the potential applicability for photodetection devices based MoTe₂ layered transition metal dichalcogenides semiconductors.

In this study, a series of SnS_2-xSe_x (0 ≤ x ≤ 2) layered semiconductors were grown by the chemical–vapor transport method. The crystal structural and material phase of SnS_2-xSe_x layered van der Waals crystals was characterized by X-ray diffraction measurements and Raman spectroscopy. The temperature dependence of the spectral features in the vicinity of the direct band edge excitonic transitions of the layered SnS_2-xSe_x compounds was measured in the temperature range of 20–300 K using the piezoreflectance (PzR) technique. The near band-edge excitonic transition energies of SnS_2-xSe_x were determined from a detailed line-shape fit of the PzR spectra. The PzR characterization has shown that the excitonic transitions were continuously tunable with the ratio of S and Se. The parameters that describe the temperature variation of the energies of the excitonic transitions are evaluated and discussed.