Carbothermal Evaporation Research Articles

Semiconducting Sn3O4 nanobelts: Growth and electronic structure

The study of structures based on nonstoichiometric SnO2−x compounds, besides experimentally observed, is a challenging task taking into account their instabilities. In this paper, we report on single crystal Sn3O4 nanobelts, which were successfully grown by a carbothermal evaporation process of SnO2 powder in association with the well known vapor-solid mechanism. By combining the structural data and transport properties, the samples were investigated. The results showed a triclinic semiconductor structure with a fundamental gap of 2.9 eV. The semiconductor behavior was confirmed by the electron transport data, which pointed to the variable range hopping process as the main conduction mechanism, thus giving consistent support to the mechanisms underlying the observed semiconducting character.

Randomly oriented ZnO nanowires grown on amorphous SiO 2 by metal-catalyzed vapour deposition

Randomly oriented ZnO nanowire (NW) networks have been grown on thermal SiO 2 substrates by the simple carbothermal reaction-assisted thermal evaporation of ZnO. One-dimensional growth was achieved with the aid of Au nanocluster catalysts dispersed on the substrates. The structures were studied by scanning electron microscopy, energy dispersive X-ray analysis, and X-ray absorption spectroscopy. The NW diameters and lengths were found to strongly depend on the substrate temperature ( T S) and to be in the 5–10 nm and 40–110 nm ranges for T S = 520 °C, and in the 50–80 nm and 1–3 μm ranges for T S = 700 °C, respectively. The growth regime was characterized by comparing the NW structures obtained on SiO 2 with those grown in the same deposition run on (1 0 0) Si substrates also covered with the Au catalyst. The NW structure prepared at 700 °C behaves as a dense NW network with net electrical conductance and persistent photoconductance. These results suggest a method to deposit size-controlled ZnO NW networks on insulating cost-effective substrates with important potential applications as in chemical sensors and solar cells.

Growth of tin oxide nanotubes by aerial carbothermal evaporation

One-dimensional nanostructures of tin oxide nanotubes were fabricated by carbothermal evaporation at 900°C in air. The synthesized film was grown on Au-coated (100) Si substrate. Heterogeneous catalysis by Au/Sn droplets assisted the formation of the tin oxide nanotubes of less than 40 nm diameter at Sn vapor pressures around 1.4×10−7 Pa. In order to reduce the nanotube diameter further, an increase in the Sn vapor pressure by changing the source materials’ ratio seemed viable.

Guided mode lasing in ZnO nanorod structures

Quasi-two-dimensional arrays of nearly parallel hexagonal ZnO nanorods and a three-dimensional cylindrical microstructure consisting of ZnO nanorods have been grown by low pressure chemical vapor deposition (CVD) and carbothermal evaporation technologies, respectively. The technology ensures high optical quality of the produced nanostructures so as to act as a gain medium for stimulated emission in the ultraviolet spectral region in combination with high quality factor laser resonators. Multiple sharp lasing peaks were realized from the produced structures under nanosecond pulse optical excitation. The lasing peaks display successive onset and saturation with increasing excitation power density in accordance with the lasing behavior of guided modes in ZnO nanorods. The produced structures are expected to find applications in integrated nanoscale optoelectronics, photonics, and sensor technologies.

Whispering gallery modes and random lasing in ZnO microstructures

Hexagonal ZnO microdiscs and hemispherical ZnO microstructure built from hierarchical nanostructures have been grown by metal?organic chemical vapour deposition and carbothermal evaporation technologies, respectively. The technologies ensure as high an optical quality of the produced structures so as to act as a gain medium for stimulated emission in the ultraviolet spectral region in combination with high quality factor laser resonators. The ZnO microdisc resonators with diameters of around 1.8??m and thicknesses of 100?nm support whispering gallery modes with a quality factor of 640, while the lasing in the hemispherical ZnO microstructure represents a combination of whispering gallery modes in microrods with a quality factor of 640?800 and random lasing in an array of ZnO nanowires with a quality factor of around 3000.

Growth mechanism and photoluminescence of the SnO2 nanotwists on thin film and the SnO2 short nanowires on nanorods

SnO2 nanotwists on thin film and SnO2 short nanowires on nanorods have been grown on single silicon substrates by using Au–Ag alloying catalyst assisted carbothermal evaporation of SnO2 and active carbon powders. The morphology and the structure of the prepared nanostructures are determined on the basis of field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), selected area electronic diffraction (SAED), high-resolution transmission electron microscopy (HRTEM), x-ray diffraction (XRD), Raman and photoluminescence (PL) spectra analysis. The new peaks at 356, 450, and 489 nm in the measured PL spectra of two kinds of SnO2 nanostructures are observed, implying that more luminescence centres exist in these SnO2 nanostructures due to nanocrystals and defects. The growth mechanism of these nanostructures belongs to the vapour–liquid–solid (VLS) mechanism.

Synthesis and Electrical Characterization of Tin Oxide Nanostructures

AbstractSn3O4 nanobelts were grown by a carbothermal evaporation process of SnO2 powders in association with the well known vapour-solid mechanism (VS). The nanobelts crystal structure was investigated by x-ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM), raman spectroscopy and field emission gun scanning electron microscopy (FEG-SEM). The structural and morphological characterization has confirmed the growth of single crystal nanobelts. The electrical characterization (current-voltage, temperature-dependent resistance curves) of individual Sn3O4 nanobelts was performed at different temperatures and light excitation. The experiments revealed a semiconductor – like character as evidenced by the resistance decreasing at high temperatures. The transport mechanism was identified as the variable range hopping.

ZnO NANORODS GROWN BY CARBOTHERMAL EVAPORATION

ZnO nanorods and bamboo-like structures were fabricated by carbothermal evaporation in Ar gas and air atmosphere on Au -coated silicon wafers. Deposition in air atmosphere led to the fabrication of nanostructured ZnO . Investigation of substrate distance from the source material revealed that thinner nanorods are grown at shorter distances.

Whispering gallery mode lasing in zinc oxide microwires

Lasing on whispering gallery modes was excited by optical pumping in single zinc oxide microwires fabricated by a simple carbothermal evaporation process. The experimentally observed laser modes agree precisely with the predicted energetic positions obtained from a plane wave model. Systematic diameter dependent measurements have been carried out for diameters of the microwires between 3 and 12μm. The investigated microlasers are found to have a lasing threshold of about 170kW∕cm2 at 10K.

Oxide-assisted growth of silicon nanowires by carbothermal evaporation

Silicon nanowires (SiNWs) have successfully been synthesized by carbothermal evaporation method. By ramping-up the furnace system at 20 °C min −1 to 1100 °C for 6 h, the vertically aligned coexist with crooked SiNWs were achieved on the silicon substrate located at 12 cm from source material. The processing parameters such as temperature, heating rate, duration, substrate position and location are very important to produce SiNWs. Morphology and chemical composition of deposited products were investigated by field-emission scanning electron microscopy (FESEM) equipped with energy dispersive X-ray analysis (EDX). The existence of small sphere silicon oxide capped nanowires suggested that the formation of SiNWs was governed by oxide-assisted growth (OAG) mechanism.

Nanostructure size evolution during Au-catalysed growth by carbo-thermal evaporation of well-aligned ZnO nanowires on (100)Si

We report the structural and morphological properties of well-aligned ZnO nanowires grown at 750 °C on Au-deposited and annealed (100)Si substrates using carbo-thermal evaporation. As-grown nanowires are made of wurtzite ZnO, have cylindrical shape and carry droplet-like nanoparticles (NPs) at their tips, as expected for vapour–liquid–solid (VLS) growth. Grazing incidence X-ray diffraction measurements demonstrate that the NPs are made of pure fcc Au. No secondary Au/Zn alloy phases were detected. Bragg diffraction patterns confirmed that the nanowires were grown with their crystal c-axes parallel to the [100] direction of Si (i.e. normal to the substrate surface), while Au NPs are mostly (111)-oriented. The diameter distribution of ZnO nanowires mimics that of the Au NPs at their tips. A quantitative study of the nanostructure size distribution after sequential annealing and growth steps evidences the occurrence of three nanoscale processes: (i) Ostwald ripening and/or coalescence of Au NPs before nanowire nucleation, (ii) Au-catalysed VLS nucleation and axial growth of ZnO nanowires and (iii) radial growth of nanowires by a vapour–solid process. These processes originate the NP and nanowire size evolution during the experiments. The present findings are interpreted in terms of Zn vapour pressure changes during carbo-thermal evaporation.

A zinc oxide microwire laser

Abstract In this paper, we report stimulated emission from a zinc oxide (ZnO) microcrystal grown by carbothermal evaporation observed by spatially resolved photoluminescence (PL) and high excitation spectroscopy (HES).

Growth and Characterization of Optical and Electrical Properties of ZnO Nano- and Microwires

ABSTRACTZnO nanowires are readily fabricated with a novel and unique, high-pressure pulsed laser deposition process developed recently by us. It allows the flexible and reproducible control of morphology, diameter, lenght and composition. Furthermore, we report on the electrical characterization as well as stimulated emission from a zinc oxide (ZnO) microcrystals grown by carbothermal evaporation observed by spatially resolved photoluminescence (PL) and high excitation spectroscopy (HES).

Growth and characterization of high-quality δ-Bi2O3 thin films grown by carbothermal evaporation

We have succeeded in the heteroepitaxial growth of a single-crystal thin film of δ-Bi2O3, which is stable at room temperature, on a YSZ substrate by carbothermal evaporation. The deposited film has no rotational in-plane domain, and the deposited film has a single crystalline phase. The film thickness is approximately 1.1 μm, and the interface of the film and the YSZ substrate is smooth. The results in this study indicate that carbothermal evaporation is suitable for the deposition of δ-Bi2O3 thin films. Further, it can be speculated that interfacial stress is crucial in the stabilization of the δ phase, indicating that the deposition as a thin film may play a role in the stabilization of δ-Bi2O3.

Growth and photoluminescence of SnO 2 nanostructures synthesized by Au–Ag alloying catalyst assisted carbothermal evaporation

One-dimensional (1D) nanowires, two-dimensional (2D) nanodendrites, and three-dimensional (3D) nanochains of SnO 2 have been grown on single silicon substrates by Au–Ag alloying catalyst assisted carbothermal evaporation of SnO 2 powders. One-dimensional twinning crystalline nanowires, 2D nanodendrites with spidery structure, and 3D nanochains with zigzag structure were reported. Three new peaks at 370, 470, and 555 nm in the measured photoluminescence spectra were observed, implying that more luminescence centers exist in SnO 2 nanostructures due to nanocrystals and defects. The growth of the SnO 2 nanostructure was discussed on the basis of the vapor–liquid–solid (VLS) mechanism.

Two-dimensional ZnO:Al nanosheets and nanowalls obtained by Al 2O 3-assisted carbothermal evaporation

Free-standing, two-dimensional ZnO nanosheets and branched honeycomb-like nanowalls have been grown together with one-dimensional nanothreads on gold covered a-plane sapphire and GaN templates on silicon substrates using Al 2O 3 assisted carbothermal evaporation of ZnO. In X-ray diffraction 2Θ−ω scans two orientations, ZnO(0001) and ZnO(10-11), of the two-dimensional nanosheets were detected. Temperature dependent cathodoluminescence shows bound exciton and donor–acceptor pair recombinations with a linewidth of 2.1 meV at 10 K. We show that the formation of the novel Al-doped ZnO nanostructures is due a vapor–liquid–solid mechanism.