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Growth of high-quality III–V nanowires at a low cost for optoelectronic and electronic applications is a long-term pursuit of research. Still, controlled synthesis of III–V nanowires using chemical vapor deposition method is challenge and lack theory guidance. Here, we show the growth of InP and GaP nanowires in a large area with a high density using a vacuum chemical vapor deposition method. It is revealed that high growth temperature is required to avoid oxide formation and increase the crystal purity of InP nanowires. Introduction of a small amount of Ga into the reactor leads to the formation of GaP nanowires instead of ternary InGaP nanowires. Thermodynamic calculation within the calculation of phase diagrams (CALPHAD) approach is applied to explain this novel growth phenomenon. Composition and driving force calculations of the solidification process demonstrate that only 1 at.% of Ga in the catalyst is enough to tune the nanowire formation from InP to GaP, since GaP nucleation shows a much larger driving force. The combined thermodynamic studies together with III–V nanowire growth studies provide an excellent example to guide the nanowire growth. [ABSTRACT FROM AUTHOR]

• Lateral growth of nanowire begins at the critical height of nanowire. • AsH 3 molar flow rate affects to the critical height of nanowire. • Arsenic trimer disturbs the reaction on the top of nanowire. InAs nanowires (NWs) were selectively grown on hole patterned InP (1 1 1)B substrate by Metal-Organic Chemical Vapor Deposition (MOCVD). This study reports the vertical growth behavior of InAs NWs transitioned at a certain height and its difference under various growth conditions. This certain height is referred as "critical height." This is a boundary where both vertical and lateral growth occur. Under this height, only vertical growth takes place. Vertical growth characteristics were reported through the determination of the critical height of NWs. The critical height was investigated for its three growth conditions; growth temperature, molar flow rates of In and As sources. Increase in growth temperature induced increase in critical height. Increase in growth temperature enhances the mobility of In adatom. This further increases diffusion length on the sidewall surface. However, increased AsH3 molar flow rate decreased the critical height. The surface reaction of In adatoms on the top (1 1 1)B surface of InAs NWs was reduced by the formation of As trimer. As a result, reduced relative vertical growth rate decreased the critical height of InAs NWs. The critical height of InAs NWs, however, was not changed by the variation of the Tri-Methyl Indium (TMIn) molar flow rate. This variation doesn't affect the mobility of In adatom on the sidewall surface or the surface reaction rate on the top (1 1 1)B surface of NWs. Hence, we concluded that variation of the mobility of In adatom on the sidewall surface and relative vertical growth rate affect the critical height of InAs NWs. [ABSTRACT FROM AUTHOR]

Growth of nanowires and etching of a substrate can be undertaken simultaneously as found during the silver droplet assisted growth of InxGa1−xAs nanowires (NWs) on Ge (100) substrates by metal organic chemical vapor deposition technique. The growth direction of free standing NWs has been found to be controlled by the size of the silver nanoparticles (AgNP). Vapor–liquid–solid growth of vertical free standing NWs on Ge (100) substrates has been found possible when the average AgNP size is 180 nm without any surface treatments or nucleation steps under experimental precursor flow rates and temperature. The NWs are found to grow in 〈011〉 and 〈111〉 direction with 120 nm average catalyst size and below that size, the AgNPs are found to etch the Ge surface instead of growing NWs. Two different kinds of etching have been observed. AgNPs of 20 nm size selectively etch the Ge (100) surface resulting in inverted pyramidal holes whereas larger AgNPs do not show any selective etching characteristics, rather create cylindrical holes. The switchover from growth to etching in smaller droplet size regime has been attributed to Gibbs–Thompson effect. The results prove the efficacy of AgNPs for simultaneous nanopatterning and nanostructure growth on Ge (100) surface. [ABSTRACT FROM AUTHOR]