Thermal vaporization and deposition of gallium oxide in hydrogen

Butt, Darryl P.; Park, Young-Soo; Taylor, T.N.

doi:10.1016/s0022-3115(98)00484-x

Cited by 83 publications

(62 citation statements)

References 10 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Consequently, the gallium loss at the surface must be largely suppressed at high p O2 . The observation goes along with that for Ga 2 O 3 reported in [78] where the partial pressure of the volatile gallium suboxide Ga 2 O decreases with increasing p O2 .…”

Section: Gallium Losssupporting

confidence: 87%

High-temperature piezoelectric crystals and devices

Fritze

2011

J Electroceram

View full text Add to dashboard Cite

Conventional piezoelectric materials such as quartz are widely used as high precision transducers and sensors based on bulk acoustic waves. However, their operation temperature is limited by the intrinsic materials properties to about 500 • C. High-temperature applications are feasible by applying materials that retain their piezoelectric properties up to higher temperatures. Here, langasite (La 3 Ga 5 SiO 14 ) and compounds of the langasite family are the most promising candidates, since they are shown to exhibit bulk acoustic waves up to at least 1400 • C. The mass sensitivity of langasite resonators at elevated temperatures is about as high as that of quartz at room temperature. Factors limiting potential use of those crystals include excessive conductive and viscous losses, deviations from stoichiometry and chemical instability. Therefore, the objective of this work is to identify the related microscopic mechanisms, to correlate electromechanical properties and defect chemistry and to improve the stability of the materials by e.g. appropriate dopants.Further application examples such as resonant gas sensors are given to demonstrate the capabilities of hightemperature stable piezoelectric materials. The electromechanical properties of langasite are determined and described by a one-dimensional physical model. Key properties relevant for stable operation of resonators are found to be shear modulus, density, electrical conductivity and effective viscosity. In order to quantify their impact on frequency and damping, a general-H. Fritze (B)

show abstract

Section: Gallium Losssupporting

confidence: 87%

High-temperature piezoelectric crystals and devices

Fritze

2011

J Electroceram

View full text Add to dashboard Cite

show abstract

“…Direct reaction of Ga and NH 3 can also result in GaN because Ga 2 O(g) can back-react with H 2 to form Ga [14,18]:…”

Section: Growth Reaction Chemistrymentioning

confidence: 99%

Self-branching in GaN Nanowires Induced by a Novel Vapor-Liquid-Solid Mechanism

2007

View full text Add to dashboard Cite

Nanowires have great potential as building blocks for nanoscale electrical and optoelectronic devices. The difficulty in achieving functional and hierarchical nanowire structures poses an obstacle to realization of practical applications. While post-growth techniques such as fluidic alignment might be one solution, selfassembled structures during growth such as branches are promising for functional nanowire junction formation. In this study, we report vapor-liquid-solid (VLS) self-branching of GaN nanowires during AuPdcatalyzed chemical vapor deposition (CVD). This is distinct from branches grown by sequential catalyst seeding or vapor-solid (VS) mode. We present evidence for a VLS growth mechanism of GaN nanowires different from the well-established VLS growth of elemental wires. Here, Ga solubility in AuPd catalyst is limitless as suggested by a hypothetical pseudo-binary phase diagram, and the direct reaction between NH3 vapor and Ga in the liquid catalyst induce the nucleation and growth. The self-branching can be explained in the context of the proposed VLS scheme and migration of Ga-enriched AuPd liquid on Ga-stabilized polar surface of mother nanowires. This work is supported by DOE Grant No. DE-FG02-98ER45701. KeywordsGallium alloys, Dissolution, Electric wire, Gallium nitride, Liquids, Nanowires, Semiconducting gallium, Vapors, AuPd alloy, GaN nanowires, Growth modes, Growth morphology, Nucleation and growth, Polar surfaces, Spontaneous reactions, Vapor-liquid-solid mechanism, VLS growth ABSTRACTInvestigations of the growth morphology of AuPd-catalyzed GaN nanowires lead us to propose a vapor-liquid-solid (VLS) mechanism distinct from the well-established VLS growth of elemental wires. Here, nucleation and growth of GaN nanowires proceeds by direct spontaneous reaction between NH 3 vapor and Ga dissolved in liquid AuPd alloy, rather than by solubilitylimited supersaturation. A frequently observed self-branching growth mode can be explained by the proposed VLS scheme and the migration of Ga-enriched AuPd liquid on Ga-stabilized polar surfaces of mother nanowires. INTRODUCTIONGaN nanowires (NWs) are of interest for nanoscale optoelectronic device applications [1][2][3][4]. Synthesis can be achieved by several methods involving vapor-liquid-solid (VLS) growth, such as thermal chemical vapor deposition (CVD) [5][6][7], hydride vapor phase epitaxy (HVPE) [8], molecular beam epitaxy (MBE) [9], and metalorganic CVD (MOCVD) [10]. The low N solubility in transition metals implies that nucleation of GaN from supersaturated catalyst droplets is unlikely, in contrast to elemental structures such as Si whiskers and NWs [11]. Here we study GaN NWs grown by thermal CVD using Ga 2 O 3 , NH 3 and AuPd catalyst. The observed morphologies suggest a VLS mechanism distinct from the nucleation and growth of elemental nanostructures from supersaturated liquid. We consider a hypothetical pseudo-binary phase diagram and thermodynamics of GaN formation reaction to propose that NW nucleation and growth occur via direct ...

show abstract

“…Therefore, H 2 can be assumed to present in our system. Ga 2 O 3 will be reduced to Ga 2 O through the following reactions [26]. The reaction of Ga 2 O with ammonia results in the formation of GaN crystal nuclei [27].…”

Section: Resultsmentioning

confidence: 99%

Fabrication of High-Density GaN Nanowires through Ammoniating Ga₂O₃/Nb Films

Zhuang

Zhang

et al. 2008

Acta Phys. Pol. A

View full text Add to dashboard Cite

High-density GaN nanowires were successfully synthesized on Si(111) substrates through ammoniating Ga 2 O 3 /Nb films under flowing ammonia atmosphere at 950• C. The as-synthesized GaN nanowires are characterized by X-ray diffraction, selected-area-electron diffraction, Fourier transform infrared, scanning electron microscopy, and field-emission transmission electron microscopy. The results show that the synthesized nanowires are singlecrystal hexagonal wurtzite GaN with diameters ranging from 30 to 100 nm and lengths up to several microns. The photoluminescence spectra measured at room temperature only exhibit a strong and broad emission peak at 367.8 nm. Finally, the growth mechanism of GaN nanowires is discussed.

show abstract

Thermal vaporization and deposition of gallium oxide in hydrogen

Cited by 83 publications

References 10 publications

High-temperature piezoelectric crystals and devices

High-temperature piezoelectric crystals and devices

Self-branching in GaN Nanowires Induced by a Novel Vapor-Liquid-Solid Mechanism

Fabrication of High-Density GaN Nanowires through Ammoniating Ga₂O₃/Nb Films

Contact Info

Product

Resources

About

Thermal vaporization and deposition of gallium oxide in hydrogen

Cited by 83 publications

References 10 publications

High-temperature piezoelectric crystals and devices

High-temperature piezoelectric crystals and devices

Self-branching in GaN Nanowires Induced by a Novel Vapor-Liquid-Solid Mechanism

Fabrication of High-Density GaN Nanowires through Ammoniating Ga2O3/Nb Films

Contact Info

Product

Resources

About

Fabrication of High-Density GaN Nanowires through Ammoniating Ga₂O₃/Nb Films