Simple Physical Vapor Deposition Research Articles

Optical properties of highly ordered AlN nanowire arrays grown on sapphire substrate

Highly ordered AlN nanowire arrays were synthesized via a simple physical vapor deposition method on sapphire substrate. The nanowires have an extremely sharp tip <10nm, with the average length around 3 μm. Raman spectroscopy analysis on the AlN nanowire arrays revealed that the lifetime of the phonons is shorter than that in bulk AlN. The transmission spectra of the AlN nanowires showed a blueshift ∼0.27eV at the absorption edge with that of the bulk AlN, which is closely related to the small size of the nanowires.

Growth temperature controlled shape variety of ZnO nanowires

ZnO nanowires array has been synthesized via a simple physical vapor deposition method at low growth temperature without using any catalyst. By controlling different growth parameters, the nanowires exhibit different shapes: needle-like with sharp tips or rod-like with flat tips. All the nanowires are single crystal with a growth direction along c-axis. The rod-like nanowires are well vertical aligned to the substrate surface with c-axis preferred orientation. The morphology difference of ZnO nanowires is believed originated from different growth mechanisms.

Synthesis of well-aligned ZnO nanowires by simple physical vapor deposition on c-oriented ZnO thin films without catalysts or additives

Well-aligned ZnO nanowires were synthesized by simple physical vapor deposition using c-oriented ZnO thin films as substrates without catalysts or additives. The synthesized ZnO nanowires have two typical average diameters: 60nm in majority and 120nm in minority. They are about 4μm in length and well aligned along the normal direction of the substrate. Most of the synthesized ZnO nanowires are single crystalline in a hexagonal structure and grow along the [001] direction. The c-oriented ZnO thin films control the growth direction. Photoluminescence spectrum was measured showing a single strong ultraviolet emission (380nm). Such result indicates that the ZnO nanowire arrays can be applied to excellent optoelectronic devices.

Synthesis of Well-aligned ZnO Nanowires Using Simple Physical Vapor Deposition without Catalysts or Additives

AbstractWell-aligned ZnO nanowires were synthesized by simple physical vapor deposition using c-oriented ZnO thin films as substrate without catalysts or additives. The synthesized ZnO nanowires have two typical average diameters: 60 nm in majority and 120 nm in minority. They are about 4ím in length and well aligned along the normal direction of the substrate. Most of the synthesized ZnO nanowires are single crystalline in a hexagonal structure and grow along the [001] direction. The c-oriented ZnO thin films control the growth direction. Photoluminescence spectrum was measured showing a single strong ultraviolet emission (380 nm). Such result indicates that the ZnO nanowire arrays can be applied to excellent optoelectronic devices.

Very large electro-optic responses in H-bonded heteroaromatic films grown by physical vapour deposition

A crucial goal for modern telecommunications systems is development of very high-speed components for broadband (>100 GHz), all-optical signal/information processing. The core component of such technologies is the electro-optic modulator, which encodes electrical signals onto fibre-optic transmissions. A significant challenge therefore is obtaining materials that have large electro-optic responses and that can be readily fabricated into devices at low cost. We report here on the realization of high-response heteroaromatic organic chromophores that can be straightforwardly self-organized from the vapour phase into intrinsically acentric, high-quality, micrometre-scale films. These pi-conjugated electro-optically active films (with second-order susceptibilities up to approximately 100 pm V(-1)) are thermally stable and conveniently grown by a simple physical vapour deposition process in a few hours. Supramolecular acentricity is achieved without electric field poling, enforced by biomimetic heterocycle-hydroxycarbonyl head-to-tail hydrogen-bonding.

Formation of ZnS nanorods by simple evaporation technique

Semiconductor nanocrystals and nanorods whose properties are largely determined by the quantum confinement effect are currently being intensively studied by materials scientists, physicists and chemists. Zinc sulphide (ZnS), a II–VI group semiconductor material possessing a direct band gap of 3.66 eV, has recently been extensively investigated due to its multifaceted applications. We report the synthesis of ZnS nanorods by a simple physical vapor deposition method and an in-detail surface analysis for device applications. Our interest in this material mainly lies behind its use as an n-window layer for our investigations on different window layers for CdTe- and CIS (Copper Indium diselenide) based solar cells and for photocatalytic production of hydrogen from water using the photocatalysts CdS/ZnS. ZnS films are deposited onto well-cleaned glass substrates at a vacuum of 5×10-5 Torr and various parameters are determined. The distance between the substrate and the source was maintained at 0.15 cm. The deposition time was about 20 min at a constant rate of evaporation and the substrates were maintained at room temperature. Structural analysis reveals the cubic nature of the crystallites, which is confirmed from atomic force microscopy (AFM) analysis. The AFM analysis reveals the formation of nanorods due to coalescence, which is substantiated from sectional analysis. A further analysis reveals the preferential growth of the nanorods and the coalescence limited by the energy in the (002) face. The composition was analyzed using an energy-dispersive X-ray method (EDX) and the film was found to possess excess sulfur. The band gap of the vacuum-deposited ZnS film was found to be 3.6 eV.

Synthesis and characterization of high-quality In 2O 3 nanobelts via catalyst-free growth using a simple physical vapor deposition at low temperature

High-quality indium oxide (In 2O 3) nanobelts were successfully synthesized without catalyst at low temperature ranged from 600 to 850 °C using a simple physical vapor deposition. To synthesize the In 2O 3 nanobelts, we employed a simple reaction of thermally evaporated indium vapor in a wet oxidizing environment. The In 2O 3 nanobelts have diameters in the range of 20–200 nm and lengths over several hundreds micrometer. The synthesized nanobelts indicate high-purity and single-crystalline cubic structure. Most of In 2O 3 nanobelts have 〈1 0 0〉 growth direction but some nanobelts have 〈1 1 0〉 growth direction. Photoluminescence spectra under excitation at 325 nm showed a strong and broad emission at 570 nm with a shoulder at 630 nm related to oxygen vacancies. We suggest that the synthesis of the In 2O 3 nanobelts follows the self-assisted growth mechanism in our method.

Low-temperature growth and Raman scattering study of vertically aligned ZnO nanowires on Si substrate

High-density ZnO nanowires (ZnONWs) were aligned onto Au-catalyzed Si substrate through a simple low-temperature physical vapor deposition method. Scanning electron microscope (SEM) observations, x-ray diffraction (XRD) analysis, and photoluminescence spectra showed that the ZnONWs were single-crystalline, with a hexagonal wurzite structure. All of the results inferred from the SEM observations, the XRD rocking curves, and the Raman spectra for the investigated samples confirm that the ZnONWs are well aligned and c-axis oriented. The Raman spectra also indicated that the ZnONWs on Si substrates are under the biaxial compressive stress. Since it takes the advantage of low-cost, easily controlled deposition spot (due to the selective deposition trait of the Au layer), potential for scale-up production, and ability to integrate with Si substrate, this technique has a potential in future for fabricating the ZnONW array-based optoelectronic devices.

Low-Temperature Growth of ZnO Nanowire Array by a Simple Physical Vapor-Deposition Method

Well-aligned single-crystalline wurzite zinc oxide (ZnO) nanowire array was successfully fabricated on an Al2O3 substrate by a simple physical vapor-deposition method at a low temperature of 450 °C. The diameter and growth rate of ZnO nanowires increased as a function of growth temperature. TEM observation showed that the ZnO nanowires were synthesized along the c-axial direction of the hexagonal crystal structure. We demonstrate that ZnO nanowires followed the self-catalyzed growth mechanism on the ZnO nuclei. Besides high-quality ZnO nanowires, sometimes a fascinating hierarchically ordered ZnO structure was also observed.

WO 3 nanorods/nanobelts synthesized via physical vapor deposition process

A simple physical vapor deposition technique, oxidizing W filaments and in situ evaporating via infrared irradiation heating at 950–1000 °C in air, was developed to prepare WO 3 one-dimensional nanostructures on Si wafers. Most of the nanostructures were nanorods with polygonal cross-sections, tens of nanometers in width. The nanorods were single-crystalline monoclinic structure, with the axes preferentially aligned along the [1 0 0] or [0 1 0] directions. In addition, some single-crystalline nanobelts of hexagonal structure were formed, with their length directions lying along the [1 1 0] direction. The formation of two different structures is discussed based on their cell parameters.

Raman characterization of epitaxial Cu–In–Se thin films

We have fabricated epitaxial chalcopyrite alloys with varying compositions and thicknesses on GaAs (001) substrates using a simple physical vapor deposition method. Growth of the films was characterized with Raman spectroscopy as well as by other analytical techniques. We identified both CuInSe 2 (001) and CuIn 3Se 5 (001). All of the spectra were dominated by the A 1(Γ 1 (1) [W 1]) non-polar optical mode at 172 cm −1 for CuInSe 2 and 152 cm −1 for the CuIn 3Se 5 phase. In addition, Raman spectra for the thinner layers indicated that these films are under compressive stress due to the lattice mismatch between the films and the substrate.

Microstructure of TiN films and interfaces formed by ion-beam-enhanced deposition and simple physical vapor deposition

The microstructure and composition of TiN films, formed by ion beam enhanced deposition (IBED) with different energy (40 keV and 90 keV) xenon ion bombardment and by simple physical vapor deposition (hereafter S-PVD) without any ion beam enhancement, and the interfaces between TiN films and Si substrates have been studied by cross-sectional view analytical electron microscopy in this work. Both the IBED TiN films prepared by Xe+ bombardment with either 40 keV or 90 keV energy ions and the S-PVD TiN film consist of nanocrystals. The TEM observations in the S-PVD case reveal an amorphous layer and a mixed layer of TiN grains and amorphous material at the TiN/Si interface. The thicknesses of the amorphous layer and the mixed layer are about 210 nm and at least 40 nm, respectively. Upon 40 keV Xe+ bombardment, an amorphous Si transition layer of about 50 nm thickness is found at the TiN/Si interface, and the TiN grains close to the TiN/Si interface are of weak preferred orientation. Upon 90 keV Xe+ bombardment, amorphous TiN and Si layers are found with a total thickness of 80 nm at the TiN/Si interface, and the TiN grains near the TiN/Si interface are of preferred orientation [111]TiN ‖ [001]Si. The energy of xenon ion bombardment has a strong effect on the microstructural characteristics of TiN films and the interfaces between the TiN films and the Si substrates, as well as the size and the preferred orientation of TiN grains.