Fabrication of Ultraviolet Photodetectors Based on Fe-Doped ZnO Nanorod Structures.

In this paper, 100 nm-thick zinc oxide (ZnO) films were deposited as a seed layer on Corning glass substrates via a radio frequency (RF) magnetron sputtering technique, and vertical well-aligned Fe-doped ZnO (FZO) nanorod (NR) arrays were then grown on the seed layer-coated substrates via a low-temperature solution method. FZO NR arrays were annealed at 600 °C and characterized by using field emission scanning microscopy (FE-SEM) and X-ray diffraction spectrum (XRD) analysis. FZO NRs grew along the preferred (002) orientation with good crystal quality and hexagonal wurtzite structure. The main ultraviolet (UV) peak of 378 nm exhibited a red-shifted phenomenon with Fe-doping by photoluminescence (PL) emission. Furthermore, FZO photodetectors (PDs) based on metal-semiconductor-metal (MSM) structure were successfully manufactured through a photolithography procedure for UV detection. Results revealed that compared with pure ZnO NRs, FZO NRs exhibited a remarkable photosensitivity for UV PD applications and a fast rise/decay time. The sensitivities of prepared pure ZnO and FZO PDs were 43.1, and 471.1 for a 3 V applied bias and 380 nm UV illumination, respectively.

Optical and structural properties of Ga-doped ZnO nanorods.

The high-density single crystalline Ga-doped ZnO nanorods were grown on a glass substrate using the hydrothermal method. The average length and diameter of the nanorods were approximately 2.36 microm and 90 nm, respectively. The Ga-doped ZnO nanorods had hexagonal wurtzite structure and a sharp morphology. The morphology and structure of nanorods were characterized by field-emission scanning electron microscopy (FESEM), high-resolution transmission electron microscope (HRTEM), X-ray diffraction (XRD) and photoluminescence (PL) spectroscopy, when the growth temperature of the nanorods was 90 degrees C, which ensured high crystalline quality.

Fabrication of Silicon Dioxide by Photo-Chemical Vapor Deposition to Decrease Detector Current of ZnO Ultraviolet Photodetectors.

Zinc oxide (ZnO)-based semiconductor is a promising application for ultraviolet photodetectors (UV PDs). The performance of ZnO UV PDs can be improved in two orientations: by reduction of the dark current and by increasing the photocurrent. In the study, we used two processes to prepare ZnO UV PDs: photochemical vapor deposition to fabricate silicon dioxide as an insulator layer and a radio frequency sputter system to prepare the ZnO film as an active layer. The results show that the silicon dioxide layer can reduce the dark current. Moreover, a large photo-dark current ratio of the metal-insulator-semiconductor (MIS) structured PD is 200 times than the metal-semiconductor-metal (MSM) structured PD. When the silicon dioxide thickness is 98 nm, we can significantly enhance the rejection ratio. The silicon dioxide layer can reduce the noise effect and enhance the device detectivity. These results indicate that the insertion of a silicon dioxide layer into ZnO PDs is potentially useful for practical applications.

Improving Field Electron Emission Properties of ZnO Nanosheets with Ag Nanoparticles Adsorbed by Photochemical Method.

Zinc oxide is a low cost and practical II-VI chemical material, which is utilized to absorb silver (Ag) nanoparticles (NPs) on zinc oxide nanosheets (ZnO NSs). Using the Ag NP-decorated ZnO NSs can improve the electrical characteristics of zinc oxide. Field electron emission characteristics of ZnO NSs and Ag-ZnO NSs indicate the turn-on fields were 5.3 and 3.2 V/µm in the dark, whereas the turn-on field were 4.3 and 2 V/µm under UV light, respectively. In addition, the field electron emission characteristics of ZnO NSs and Ag-ZnO NSs indicate the enhanced field enhancement factors were 3002 and 3420 in the dark and 3276 and 4815 under UV light, respectively.

Bending effects of ZnO nanorod metal-semiconductor-metal photodetectors on flexible polyimide substrate.

The authors report the fabrication and I-V characteristics of ZnO nanorod metal-semiconductor-metal photodetectors on flexible polyimide substrate. From field-emission scanning electron microscopy and X-ray diffraction spectrum, ZnO nanorods had a (0002) crystal orientation and a wurtzite hexagonal structure. During the I-V and response measurement, the flexible substrates were measured with (i.e., the radius of curvatures was 0.2 cm) and without bending. From I-V results, the dark current decreased, and the UV-to-visible rejection ratio increased slightly in bending situation. The decreasing tendency of the dark current under bending condition may be attributed to the increase of the Schottky barrier height.

InN nanorods prepared with CrN nanoislands by plasma-assisted molecular beam epitaxy.

The authors report the influence of CrN nanoisland inserted on growth of baseball-bat InN nanorods by plasma-assisted molecular beam epitaxy under In-rich conditions. By inserting CrN nanoislands between AlN nucleation layer and the Si (111) substrate, it was found that we could reduce strain form Si by inserting CrN nanoisland, FWHM of the x-ray rocking curve measured from InN nanorods from 3,299 reduced to 2,115 arcsec. It is due to the larger strain from lattice miss-match of the film-like InN structure; however, the strain from lattice miss-match was obvious reduced owing to CrN nanoisland inserted. The TEM images confirmed the CrN structures and In droplets dissociation from InN, by these results, we can speculate the growth mechanism of baseball-bat-like InN nanorods.