Selective growth of ZnSe and ZnCdSe nanowires by molecular beam epitaxy (original) (raw)

Low-temperature synthesis of ZnSe nanowires and nanosaws by catalyst-assisted molecular-beam epitaxy

Applied Physics Letters, 2005

Single-crystal ZnSe nanowires are grown on a prepatterned gold catalyst by molecular-beam epitaxy. Optimum selectivity and maximum nanowire densities are obtained for growth temperatures in the range 400-450°C, but gold-assisted growth is demonstrated for temperatures as low as 300°C. This suggests a diffusion process on/through the catalyst particle in the solid state, in contrast to the commonly assumed liquid phase growth models. Straight wires, as thin as 10 nm, nucleate together with thicker and saw-like structures. A gold particle is always found at the tip in both cases.

Growth of ZnSe nanowires by molecular beam epitaxy

4th IEEE Conference on Nanotechnology, 2004., 2004

I 4 Absnaci -We have grown ZnSe nanowires on Au-coated SiOl by molecular beam epitaxy. Data are reported for structures grown at 450 and 550 OC. High resolution electron microscopy shows that the lower growth temperature gives rise to a higher density of high-quality nanostructures and that nanowires, nanobelts and nanusaws are all present in our samples. ZnSe nanostructures do not grow on the noncoated substrate. Photoluminescence shows a blue component in samples grown at lower temperature.

Epitaxial growth of ZnSe and ZnSe/CdSe nanowires on ZnSe

physica status solidi (c), 2010

We report the molecular beam epitaxy (MBE) growth of ZnSe nanowires (NWs) on a ZnSe(100) epilayer assisted by gold catalyst. Gold dewetting assists in the formation of nanotrenches along the [0-1-1] direction in the ZnSe buffer layer. Nucleation of the gold catalyst in the trenches leads to the growth of NWs preferentially in directions orthogonal to the trenches. The wires adopt mostly the wurtzite type structure and grow along the caxis. CdSe quantum dots were inserted in the ZnSe NWs. The CdSe insertions systematically adopt a cubic zincblende arrangement with a [111] growth axis, as confirmed by transmission electron microscopy.

Temperature-Dependent Growth Direction of Ultrathin ZnSe Nanowires

Small, 2007

Semiconductor nanowires (NWs) are promising candidates for applications in nanoscale electronic and optoelectronic devices. In recent years, much effort has been devoted to synthesizing NWs with controlled morphology and structure using various approaches, for example, laser-assisted chemical vapor deposition (CVD), [1] oxide-assisted CVD, [2] thermal CVD, [3-8] metal-catalyzed molecular beam epitaxy (MBE) [9-12] and chemical beam epitaxy (CBE). [13] Among these techniques, the metal-catalytic (also called the vapour-liquid-solid (VLS) [14]) growth method offers a number of advantages. For example, it can produce freestanding NWs with fully controlled diameters because the nucleation sites and the diameters of the NWs can be wellcontrolled by the preformed metal catalysts. For most semiconductor NWs with large diameters, the growth directions are generally specific and easily controlled. However, ultrathin NWs often display various growth directions. The lattice orientation in ultrathin semiconductor NWs is important because it may affect the optical and transport properties of the NW. [15, 16] In previous studies, several growth directions, such as < 111 > , [1] < 112 > , [2, 10] and < 110 > , [6, 10, 11, 15] have frequently been observed in ultrathin semiconductor NWs grown by different techniques. The mechanisms for the formation of NWs with varied orientations are not fully understood, mainly due to a lack of appropriate characterization. Theoretical analyses have shown that the growth directions of NWs may depend on the synthesis conditions, surface states (e.g., the presence of oxygen or impurities), and defect structures (e.g., surface steps and dislocations). [17] We have reported the synthesis of II-VI semiconductor NWs based on Au-catalyzed VLS MBE. [10] The MBE technique provides an ideal clean growth environment in which the atomic structure, impurity, and doping state can be easily controlled. We observed that ultrathin ZnSe (or ZnS)

Catalytic growth of ZnTe nanowires by molecular beam epitaxy: structural studies

Nanotechnology, 2007

ZnTe nanowires were grown by molecular beam epitaxy on GaAs substrates of three different orientations: (100), (110), and (111)B. The catalyst droplets were produced through in situ annealing of a previously deposited Au layer and by forming the eutectic alloy with Ga from the substrate. The influence of substrate orientation and growth parameters on the properties of nanowires was investigated using scanning and transmission electron microscopy, energy dispersive x-ray spectroscopy, and x-ray diffraction. The growth process was based on the vapour-liquid-solid mechanism and the contribution of the diffusion-induced effect in this mechanism was confirmed by correlating the length and the diameter of the produced nanowires. The nanowires had diameters ranging from 30 to 70 nm and lengths between 1 and 2 μm. The growth axis of the nanowires was 111 and the nanowires grew along 111 directions of the substrate, independent of the substrate orientation used. The nanowires had stacking faults at the bottom and those grown at optimal conditions possessed perfect cubic structure near the top.

Catalyst incorporation in ZnSe nanowires

Philosophical Magazine Letters, 2006

ZnSe nanowires, 5-10 nm wide and several microns long, were fabricated by Au-catalyzed molecular beam epitaxy. Specially designed silicon-silicon dioxide substrates allowed an examination of individual nanowires with a combination of phase-contrast high-resolution transmission electron microscopy, Z-contrast scanning transmission electron microscopy imaging and energy-dispersive X-ray spectroscopy using a low-current electron probe with a diameter of 0.2 nm. Experimental results demonstrate direct evidence of Au incorporation within single-crystal sphalerite ZnSe nanowires.

MBE Growth and Properties of ZnTe- and CdTe-Based Nanowires

Journal of the Korean Physical Society, 2008

We review our results on the growth of ZnTe-and CdTe-based nanowires (NWs) and on their basic structural and optical properties. The nanowires were produced by using molecular beam epitaxy (MBE) with the use of a mechanism of catalytically-enhanced growth. The growth of ZnTe, CdTe, ZnMgTe and ZnMnTe nanowires was performed from elemental Zn, Cd, Mn, Mg and Te sources on the surfaces of (001)-, (110)-and (111)B-oriented GaAs substrates with Au nanocatalysts. The morphological and structural properties of the nanowires were assessed by using X-ray diffractometry, field-emission scanning electron microscopy, and high resolution transmission electron microscopy. Additional studies of the compositions of both the nanowires and the Au-rich nanocatalysts were performed with the use of energy dispersive X-ray spectroscopy. The optical properties of the NWs were assessed by using photoluminescence and Raman-scattering studies performed in both macro and micro modes. The studies revealed that binary and quaternary nanowires with average diameters from 30 to 70 nm and lengths from 1 to 2.6 µm were monocrystalline in their upper parts, their growth axis was 111 , and they grow along the [111] direction of the substrate, independent of the substrate orientation used. A Au-rich (with 20 % Ga) spherical nanocatalyst was always visible at the tip of a nanowire, thus indicating that a vapor-liquid-solid mechanism was responsible for the growth of the ZnTe-and the CdTe-based nanowires. The formation of homogeneous mixed crystal ZnMnTe and ZnMgTe nanowires was demonstrated by measurements of the variation of the lattice constant and by Raman experiments that revealed the expected shift and appearance of new phonon lines and a strong enhancement of the LO-phonon structures for an excitation close to the exciton energy of the NW materials. The photoluminescence from the internal Mn 2+ transition between crystal-field-split energy levels (4 T1 → 6 A1) was observed in the ZnMnTe nanowires.

ZnSe/ZnCdSe heterostructure nanowires

Journal of Crystal Growth, 2010

The authors report the growth of high density ZnSe/ZnCdSe heterostructure nanowires on oxidized Si substrate. It was found that the as-grown nanowires were tapered with mixture of cubic zinc-blende and hexagonal wurtzite structures. It was also found that photoluminescence intensities observed from these ZnSe/ZnCdSe heterostructure nanowires were much larger than observed from the homogeneous ZnSe nanowires. Furthermore, it was found that activation energies for the nanowires with well widths of 6, 12, 18 and 24 nm were 22, 41, 67 and 129 meV, respectively.

Substrate-Dependent Differences in the Crystal Structures and Optical Properties of ZnSe Nanowires

Journal of Nanomaterials, 2015

The optical and structural properties of ZnSe nanowires directly grown on three different substrates, SiO2, ITO, and graphene, were investigated. ZnSe nanowires grown on graphene and SiO2were found to have cubic structures, while ZnSe nanowires grown on ITO had a mixed cubic and hexagonal structure. The main peaks in the photoluminescence spectra of ZnSe nanowires grown on SiO2, ITO, and graphene were located at 459, 627, and 627/460 nm, respectively. In addition, a field-emission light-emitting device was fabricated using ZnSe nanowires as a phosphor and graphene as an electrode. The device showed a red emission peak with Commission Internationale de L’Eclairage coordinates of (0.621, 0.315).