InN Powder Research Articles

Generation of ultra-small InN nanocrystals by pulsed laser ablation of suspension in organic solution

Nanostructures of InN have been extensively investigated since nano-size provides a number of advantages allowing applications in nanoscale electronic and optoelectronic devices. It is quite important to obtain pure InN nanocrystals (InN-NCs) to reveal the characteristic features, which gain interest in the literature. Here, we proposed a new approach for the synthesis of ultra-small hexagonal InN-NCs by using suspension of micron-sized InN powder in ethanol with pulsed laser ablation method. The liquid environment, laser energy and ablation time were optimized and a post-synthesis treatment, centrifugation, was performed to achieve InN-NCs with the smallest size. Besides, the micron-sized InN powder suspension, as a starting material, enabled us to obtain InN-NCs having diameters smaller than 5 nm. We also presented a detailed characterization of InN-NCs and demonstrated that the formation mechanism mainly depends on the fragmentation due to laser irradiation of the suspension.

Composition-dependent electronic properties of indium–zinc–oxide elongated microstructures

Microrods and hierarchical structures of indium–zinc–oxide (IZO) with different compositions were grown by thermal treatments of mixtures of InN and ZnO powders. In long rods, an increase in Zn content along the growth axis is revealed by energy dispersive spectroscopy. The structures obtained range from Zn-doped indium oxide with a few atomic per cent of Zn, to IZO compounds of the type ZnkIn2Ok+3. X-ray photoelectron spectroscopy measurements with spatial resolution show that IZO microstructures degenerate at room temperature, with carrier concentration of the order of 1020cm−3. Electron accumulation has been found for undoped (100) and (111) surfaces, whereas depletion of carriers at the surface is observed in IZO samples. The Fermi level position correlates with the Zn concentration at the surface which, taking into account the surface dependence of the ionization potentials, work functions and band gaps, could lead to tunable material properties for device applications. Cathodoluminescence emission intensity is enhanced by the presence of Zn, which induces spectral changes and broadening of the emission band compared with undoped material. The results are discussed in terms of the charge neutrality level and the band structure of the material.

Indium Zinc Oxide Pyramids with Pinholes and Nanopipes

Micropyramids of zinc-doped indium oxide have been grown by thermal treatments of compacted InN and ZnO powders at temperatures between 700:and 900 degrees C Under argon flow. X-ray diffraction (XRD) measurements and energy-dispersive X-ray (EDS) mappings as well as local EDS spectra enable the identification of rough surfaces of the pyramids with the nucleation of a shell of nanocrystallites with high Zn/In ratio because of the formation of Zn(k)In(2)O(k+3). Some of the pyramids have a truncated tip with pinholes with regular crystalline facets. The apexes of these pinhole's present a hollow core or nanopipe The possible relation of the nanopipes with a dislocation driven growth is discussed. A growth model is proposed from the morphology evolution of the pyramids during the formation of the In(2)O(3)-ZnO (IZO) compound X-ray photoelectron spectroscopy and microscopy (XPS-ESCA) Measurements are used to discuss the Zn incorporation as a dopant and the formation of Zn(k)In(2)O(k+3) ternaries. Cathodoluminescence (CL) in the scanning electron microscopy (SEM) shows a dependence of the luminescence of the microstructures on the Zn concentration and the growth temperature.

Micro- and Nanopyramids of Manganese-Doped Indium Oxide

Mn-doped In2O3 nanopyramids have been grown by a catalyst-free thermal process at 700 °C using InN and Mn2O3 powders as precursors. Energy dispersive spectroscopy, as well as X-ray photoelectron spectroscopy, demonstrate the presence of Mn in the pyramids in a content below 1 at. %. In addition to pyramids, nanowires with diameters of about 100 nm grow during treatments at 800 °C. Luminescence has been studied by cathodoluminescence in the scanning electron microscope, showing emissions at 1.9, 2.65, and 3.3 eV. Dopant incorporation into the nanostructures and their oxidation states, as well as the effect on the electronic structure, have been measured and discussed.

Indium Tin Oxide Micro- and Nanostructures Grown by Thermal Treatment of InN/SnO2

Mixtures of InN and SnO2 powders, with a weight ratio of 10:1, have been used as precursors for the thermal growth of arrow-shaped and other elongated micro- and nanostructures of indium−tin oxide (ITO) containing about 2.6 atom % of Sn. The temperatures used in the process, in the range 650−750 °C, favor the decomposition of InN and oxidation of In, with a limited incorporation of Sn in the resulting compound. Arrow-shaped indium−tin oxide structures are obtained and formation of stannates during the process is avoided. X-ray photoelectron spectroscopy indicates that tin incorporates into the In2O3 lattice mainly as Sn4+. Luminescence of the ITO microstructures has been studied by cathodoluminescence in the scanning electron microscope.

Self-Assembled Growth of InN Microcages and Nanowires by Ammonolysis of an Amorphous Precursor and Their Optical Properties

Microcages and nanowires of InN were synthesized by ammonification of an indium precursor in the temperature range 650―700 °C. The phases of the ammonified products were identified through X-ray diffraction (XRD). Morphology and crystal structure of the samples were determined through field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), and high resolution transmission electron microscopy (HRTEM) analysis. The thermal behavior of the precursor and synthesized InN powder was investigated using thermogravimetric analysis (TGA). The growth mechanism for the formation of different morphologies at various experimental conditions is explained on the basis of diffusion and vapor-solid process following least action principle. Large blue shift (1―1.5 eV) in the apparent band gap was observed with the increase of reaction time. The contributions of refractive index and the existence of three simultaneous direct transitions at 0.8, 1, 1.4 eV were identified from the optical absorption spectra. Electrical measurements were carried out to obtain a band gap of 1.25 eV in the sample.

Three dimensional nanowire networks and complex nanostructures of indium oxide

Elongated In2O3 micro- and nanostructures have been grown by two-step thermal treatments of compacted InN powder, at temperatures between 350 and 700°C. Different thermal treatments have been found to induce the growth of structures with different sizes and morphologies as wires, rods, or arrows. The experimental conditions leading to the different structures, as well as the evolution of the structures during the treatments, have been investigated. Some treatments lead to large scale formation of three dimensional networks of the mentioned structures. The mechanism of network formation is discussed. The structures have been characterized by cathodoluminescence, scanning electron microscopy, and x-ray diffraction.

Growth and luminescence of elongated In2O3 micro- and nanostructures in thermally treated InN

Indium oxide elongated micro- and nanostructures have been grown by thermal treatment of InN powder. Chains of nanopyramids connected by nanowires, forming a necklace-like structure, as well as cubes and arrow-like structures consisting of a long rod with a micron size pyramid on the top, grow at temperatures in the range 600–700°C in a catalyst free process. The structures have been characterized by scanning electron microscopy and cathodoluminescence.

Low-temperature solvothermal synthesis of nanocrystalline indium nitride and Ga–In–N composites from the decomposition of metal azides

Nanocrystalline InN powders have been synthesized through metal azide decomposition in superheated toluene and refluxing hexadecane solvents near 280 °C. The metal azide intermediates were formed in situ through the metathesis reaction of InBr3 and NaN3. The InN products from toluene consist of ∼10 nm hexagonal (wurtzite) structured crystallites in aggregated arrangements. InN from hexadecane and lower temperature toluene reactions produced more poorly crystalline InN that appears to contain a cubic (zinc blende) component. Coordinating amine solvents led to decomposition of the nitride to indium metal. Several reactions were undertaken to produce mixed metal nitrides of the form Ga1−zInzN where z is 0.5 and 0.75. The mixed metal nitride products are analytically consistent with composite versus solid-solution formation, however some metal mixing is observed. Data from X-ray diffraction, electron microscopy, thermal analysis, elemental analysis, and several spectroscopic methods are combined to form a consistent picture of the bulk and surface structures for these nanocrystalline InN materials.

Optical properties of indium nitride powder and films

Using photoluminescence and transmission measurements, we have studied the optical properties of indium nitride powder and thin films grown by molecular beam epitaxy. The bandgap for InN powder with electron concentration ∼ 4·1019 cm−3 was 0.94 eV, and for InN films with electron concentrations ∼1018 cm−3 it was 0.7 eV. We have established that when the electron concentration is increased to 8·1019 cm−3, the bandgap of InN increases to 1.0 eV. The change in the bandgap as a function of the concentration is due to the appearance of the Burstein-Moss effect.

Thermodynamics and phase stability in the In–N system

Results of a chemical vapor deposition crystal growth method intended to produce large amounts of InN needed for thermodynamic experiments are reported. Polycrystalline films of InN were grown by reaction of InCl3 and NH3 in a hot-wall silica reactor under nearly atmospheric pressure. Samples were analyzed using x-ray diffraction and chemical analysis. The decomposition of InN was studied in both thin film and powder form. InN films were investigated by isothermal heating under nitrogen and subsequent microscopic inspection. The removal of the nucleation barrier of forming the first liquid phase was emphasized. InN powder decomposition experiments involved two different customized thermogravimetric methods: (i) dynamic oscillation thermogravimetric analysis (TGA), and (ii) isothermal stepping TGA for a higher resolution of the decomposition start. The decomposition start was found consistently at (773 ±5) K under 1 bar of nitrogen. Nevertheless, it is suggested that InN may be metastable even below room temperature based on Computer Coupling of Phase Diagrams and Thermo chemistry-type thermodynamic analysis of all available phase equilibrium and thermodynamic data. This included the determination of the absolute entropy of InN, 31.6 ±3 J/mol-formula K, based on a Debye and Einstein analysis of the experimental data on the heat capacity. All calculations of pressure are corrected for the fugacity of nitrogen, which becomes crucial above 1000 bar. The contradictory literature data in the In–N system are discussed based on three different internally consistent thermodynamic analyses of the system that highlight the consequences of different choices made on the decomposition temperature of InN. Widely reproduced data in the literature are shown to produce thermodynamically impossible negative absolute entropy of InN. Complete P-T-x phase diagrams are given, which strongly suggest that solid InN is metastable under ambient conditions. To find out that InN crystals could be reproducibly superheated more than 500 K before they actually decompose comes as a surprise compared to other III-V systems, especially Ga–N.

Preparation of ultrafine InN powder by the nitridation of In2O3 or In(OH)3 and its thermal stability

Crystalline InN powder has been prepared by the nitridation of In2O3 and In(OH)3 with NH3 gas for the first time, and ultrafine InN powder in the size range 50–300 nm and with a specific surface area of 8 m2 g−1 has been obtained using In2O3 nanoparticles as the starting material. The resulting powders were characterized by XRD, FE-SEM, TEM, TG-DSC and BET surface area techniques. It was found that nanosized In2O3 was completely converted into InN at 600 °C within 8 h. The thermal stability of the ultrafine InN powder in air and under a nitrogen atmosphere was also investigated. It was observed that InN began to be oxidized into In2O3 at 389 °C and decomposed in the narrow temperature range of 595–696 °C in flows of air and N2, respectively.

Lattice parameters, density and thermal expansion of InN microcrystals grown by the reaction of nitrogen plasma with liquid indium

Abstract InN crystals of size up to 50 μm were synthesized using a microwave plasma source of nitrogen. The InN powder of wurtzite-type structure obtained was characterized by X-ray diffraction. Lattice parameters were measured in the temperature range 100–673 K. The average room-temperature lattice parameters of three of the samples studied at 296(±3)K are a = 3.5374(1)Å, c = 5.7027(5)Å. The calculated density is 6.923 ± 0.003g cm−3. The thermal expansion coefficients in the temperature range investigated are a a = 3.6(2) × 10−6K−1 and a c = 2.6(3) × 10−6K−1.

Comparison of GaN, InN and AlN powders for susceptor-based rapid annealing of group III nitride materials

We have compared the use of GaN, InN and AlN powders for providing a nitrogen partial pressure within a graphite susceptor during high-temperature rapid thermal annealing of GaN, AlN, InN and InAlN. At temperatures above vapour transport of In from InN powder produces In droplet condensation on the surface of all nitride samples being annealed. GaN powder provides better surface protection than AlN powders for temperatures up to when annealing GaN and AlN samples. Dissociation of nitrides from the surface is found to occur with approximate activation energies of 3.8 eV, 4.4 eV and 3.4 eV, respectively, for GaN, AlN and InN.

High temperature annealing of GaN, InN, AlN and related alloys

Transient thermal processing is employed for implant activation, contact alloying, implant isolation and dehydrogenation during III-nitride device fabrication. We have compared use of InN and AlN powder as methods for providing a N 2 partial pressure within a graphite susceptor for high temperature annealing of GaN, InN AlN, InAlN and InGaN. The AlN powder provides adequate surface protection to temperatures of ∼ 1100°C for AlN, ≥ 1050°C for GaN, ∼ 600°C for InN and ∼ 800°C for the ternary alloys. While the InN powder provides a higher N 2 partial pressure than AlN powder, at temperatures above ∼ 750°C the evaporation of In is sufficiently high to produce condensation of In droplets on the surfaces of the annealed samples.

Rapid thermal processing of III-nitrides

High-temperature annealing is necessary in a number of applications for III-nitrides, including activation of Si+ or Mg+ implants for doping, maximization of implant-isolated regions, and Ohmic contact sintering. We have compared two methods for protection against surface dissociation of GaN, AlN, InN, InxGa1−xN, and InxAl1−xN during rapid thermal processing in N2 ambients. In the first method, AlN or InN powder is placed in the reservoirs of a SiC-coated graphite susceptor and provides a N2 overpressure for the nitride samples within the susceptor. In the second method, the nitrides are placed face down on other III–V substrates during annealing. In both techniques N loss from the nitride surface is found to occur at ⩾1050 °C for GaN and ⩾1100 °C for AlN and ⩾InN, as measured by Auger electron spectroscopy. Real surface roughening is generally significant only for the In-containing materials, with GaN and AlN retaining smooth morphologies even up to 1150 °C unless H2 is present in the annealing ambient. When InN powder is used in the susceptor, there is In droplet condensation on the surfaces of all samples above ∼750 °C leading to higher root-mean-square surface roughness measured by atomic force microscopy. The N2-deficient surfaces of the binary nitrides become strongly n type, while those of ternaries become less conducting. At temperature of 850–900°C, the In droplets on thermally degraded ternaries also begin to evaporate, leading to an apparent improvement in morphology. The presence of H2 or O2 in the annealing ambient lowers the dissociation temperature of each of the nitrides by 100–200 °C, due to an enhancement in N2 removal.

Rapid Thermal Processing of III-Nitrides

ABSTRACTTransient thermal processing is employed for implant activation, contact alloying, implant isolation and dehydrogenation during III-nitride device fabrication. We have compared use of InN, AlN and GaN powder as methods for providing a N2 overpressure within a graphite susceptor for high temperature annealing of GaN, InN, A1N and InAlN. The AlN powder provides adequate surface protection to temperatures of ∼1100°C for AlN, > 1050°C for GaN, ∼600°C for InN and ∼800°C for the ternary alloy. While the InN powder provides a higher N2 partial pressure than AlN powder, at temperatures above ∼750°C the evaporation of In is sufficiently high to produce condensation of In droplets on the surfaces of the annealed samples. GaN powder achieved better surface protection than the other two cases.

InN Thermodynamics and Crystal Growth at High Pressure of N2

InN is a wide direct gap semiconductor, which has not been yet grown in the form of large single crystals. In this work, we report the first synthesis and crystallization of InN from its constituent elements. We have also calculated p-T stability curve for this compound, up to 20 kbar, using low pressure decomposition data1) and equation of state of N22). We verified this curve by crystal growth experiments as well as by DTA measurements of decomposition of InN powder at high N2 pressure up to 14 kbar. InN crystals are characterized by SEM and optical absorption.