The III nitrides have been intensely studied in recent years because of their huge potential for everything from high-efficiency solid-state lighting and photovoltaics to high-power and temperature electronics. In particular, the InGaN ternary alloy is of interest for solid-state lighting and photovoltaics because of the ability to tune the direct bandgap of this material from the near-ultraviolet to the near-infrared region. In an effort to synthesize InGaN nitride, researchers have tried many growth techniques. Nonetheless, there remains considerable difficulty in making high-quality InGaN films and/or freestanding nanowires with tunability across the entire range of compositions. Here we report for the first time the growth of single-crystalline In(x)Ga(1-x)N nanowires across the entire compositional range from x=0 to 1; the nanowires were synthesized by low-temperature halide chemical vapour deposition and were shown to have tunable emission from the near-ultraviolet to the near-infrared region. We propose that the exceptional composition tunability is due to the low process temperature and the ability of the nanowire morphology to accommodate strain-relaxed growth, which suppresses the tendency toward phase separation that plagues the thin-film community.
Data provided are for informational purposes only. Although carefully collected, accuracy cannot be guaranteed. The impact factor represents a rough estimation of the journal's impact factor and does not reflect the actual current impact factor. Publisher conditions are provided by RoMEO. Differing provisions from the publisher's actual policy or licence agreement may be applicable.
"One-dimensional (1D) nanostructures, such as nanorods [11,12], nanotubes [13e16], and nanowires [17,18], which have smaller diffusion distance of carriers and larger surface areas, are expected to have improved charge separation, charge transport, and light absorption properties compared to TiO 2 thin films with a planar structure. The methods to fabricate 1D TiO 2 nanostructures include colloidal synthesis [19,20], electrodeposition  , organometallic chemical vapor deposition (OMCVD) [22,23], chemical vapor deposition (CVD) [24,25], oblique-angle deposition (OAD) , hydrothermal processes [26,27]. Besides, one unique method for the fabrication and tailoring of nanostructured materials is via ion beam modification . "
[Show abstract][Hide abstract]ABSTRACT: In this work, well-ordered nanorods were fabricated on the surface of TiO2 thin films deposited on Ti sheets by an ion irradiation method using nitrogen ion irradiation with the energy of 65 keV to a fluence of 1 × 1017 ions/cm2. These TiO2 nanorods are about 120 nm in length and 20–40 nm in diameter. After post-irradiation annealing at 500 °C in O2, the nanorod array photoelectrode displays largely enhanced performance for photoelectrochemical (PEC) water splitting compared to that of the un-irradiated TiO2 thin films with a planar structure. The influences of the irradiated ion energy on the morphology and photocurrent density of the nanorods were investigated. The 65 keV N+ irradiated TiO2 thin films shows a higher photocurrent density than those of the 45 and 85 keV N+ irradiated TiO2 thin films. We also discussed the influence of annealing conditions on the PEC performance of TiO2 nanorods, and it was found that the nanorods annealed at 600 °C in vacuum produce a much higher photocurrent density of 0.6 mA/cm2 at 0.8 V (vs. a saturated calomel electrode), which is about 7 times higher than that of the nanorods annealed in oxygen. This work proposes that ion irradiation combination with thermal annealing in vacuum could be an effective approach for developing nanostructured materials for water splitting.
Full-text · Article · Apr 2015 · International Journal of Hydrogen Energy
"To overcome these problems, alternative methods of band gap tuning in GaN through equibiaxial in-plain strains have been proposed re- cently  as a method of " strain engineering " . In the context of GaN based nano-materials, nanowires, nanotubes, and nanospirals of GaN have been synthesized which showed great potential for fabricating wide-spectrum LEDs and other nano-scale devices567. In particular, a density functional theory (DFT) study in 2006  predicted that when the layer number of (0001)-oriented WZ materials (e.g., AlN, BeO, GaN, SiC, ZnO, and ZnS) is small, the wurtzite structures transform into a new form of stable hexagonal graphite-like or hexagonal boron nitride (BN)-like structure. "
[Show abstract][Hide abstract]ABSTRACT: We present ab initio calculations on the effect of in-plane equi-biaxial
strain on the structural and electronic properties of hypothetical
garphene-like GaN monolayer (ML-GaN). It was found that ML-GaN got buckled for
compressive strain in excess of 7.281 %; buckling parameter increased
quadratic-ally with compressive strain. The 2D bulk modulus of ML-GaN was found
to be smaller than that of graphene and graphene-like ML-BN, which reflects
weaker bond in ML-GaN. More importantly, the band gap and effective masses of
charge carriers in ML-GaN were found to be tunable by application of in-plane
equi-biaxial strain. In particular, when compressive biaxial strain of about 3
% was reached, a transition from indirect to direct band gap-phase occurred
with significant change in the value and nature of effective masses of charge
carriers; buckling and tensile strain reduced the band gap - the band gap
reduced to 50 % of its unstrained value at 6.36 % tensile strain and to 0 eV at
an extrapolated tensile strain of 12.72 %, which is well within its predicted
ultimate tensile strain limit of 16 %. These predictions of strain-engineered
electronic properties of highly strain sensitive ML-GaN may be exploited in
future for potential applications in strain sensors and other nano-devices such
as the nano-electromechanical systems (NEMS).
"High vacuum chemical vapour deposition (HV-CVD) provides several interesting features involving addressable combinatorial experiments for fast optimization of thin films            , controlled growth of nanowires in a vapour–liquid–solid (VLS) process   , and selective area growth exploiting laser   , ion , or electron  beam assisted depositions. "
[Show abstract][Hide abstract]ABSTRACT: Chemical vapour deposition (CVD) processes depend on the availability of suitable precursors. Precursors that deliver a stable vapour pressure are favourable in classical CVD processes, as they ensure process reproducibility. In high vacuum CVD (HV-CVD) process vapour pressure stability of the precursor is of particular importance, since no carrier gas assisted transport can be used. The dimeric Nb2(OEt)10 does not fulfil this requirement since it partially dissociates upon heating. Dimethylamino functionalization of an ethoxy ligand of Nb(OEt)5 acts as an octahedral field completing entity and leads to Nb(OEt)4(dmae). We show that Nb(OEt)4(dmae) evaporates as monomeric molecule and ensures a stable vapour pressure and, consequently, stable flow. A set of HV-CVD experiments were conducted using this precursor by projecting a graded molecular beam of the precursor onto the substrate at deposition temperatures from 320 °C to 650 °C. Film growth rates ranging from 8 nm · h- 1 to values larger than 400 nm · h- 1 can be obtained in this system illustrating the high level of control available over the film growth process. Classical CVD limiting conditions along with the recently reported adsorption-reaction limited conditions are observed and the chemical composition, microstructural and optical properties of the films are related to the corresponding growth regime. Nb(OEt)4(dmae) provides a large process window of deposition temperatures and precursor fluxes over which carbon-free and polycrystalline niobium oxide films with growth rates proportional to precursor flux are obtained. This feature makes Nb(OEt)4(dmae) an attractive precursor for combinatorial CVD of niobium containing complex oxide films that are finding an increasing interest in photonics and photoelectrochemical water splitting applications. The adsorption-reaction limited conditions provide extremely small growth rates comparable to an atomic layer deposition (ALD) process indicating that HV-CVD has the potential to be an alternative to ALD for growth of ultrathin films on low aspect ratio substrates.