We present growth studies of InSb nanowires grown directly on [Formula: see text] and [Formula: see text] substrates. The nanowires were synthesized in a chemical beam epitaxy (CBE) system and are of cubic zinc blende structure. To initiate nanowire nucleation we used lithographically positioned silver (Ag) seed particles. Up to 87% of the nanowires nucleate at the lithographically pre-defined positions. Transmission electron microscopy (TEM) investigations furthermore showed that, typically, a parasitic InSb thin film forms on the substrates. This thin film is more pronounced for InSb((111)B) substrates than for InAs((111)B) substrates, where it is completely absent at low growth temperatures. Thus, using InAs((111)B) substrates and growth temperatures below 360 °C free-standing InSb nanowires can be synthesized.

Oxide and nitride nanotubes have gained attention for their large surface areas, wide energy band gaps, and hydrophilic natures for various innovative applications. These nanotubes were either grown by templates or multistep processes with uncontrollable crystallinity. Here the authors show that single crystal ZnO nanotubes can be directly grown on planar substrates without using catalysts and templates. These results are guided by the theory of nucleation and the vapor-solid crystal growth mechanism, which is applicable for transforming other nanowires or nanorods into nanotubular structures.

Among all known semiconductors, bulk InSb has the highest electron mobility of 77000 cm 2 3 V À1 3 s À1 , along with a sizable hole mobility of 850 cm 2 3 V À1 3 s À1 . 1,2 This makes InSb a promising candidate for high-speed, low-power electronics. 3 Besides, InSb has the largest lattice constant (a 0 = 0.648 nm) and the smallest band gap (0.17 eV) among the IIIÀV semiconductors, with the latter qualifying InSb for IR emission and detection. 4 Moreover, InSb is an excellent candidate for spinrelated and quantum-effect studies due to its large g-factor and the huge exciton Bohr radius of 60 nm. 5 Another outstanding property of InSb is its large thermoelectric figure-of-merit of 0.6, which furthermore increases with smaller feature sizes. 6,7 In general, IIIÀV materials crystallize in either the cubic zinc blende or the polytypic hexagonal wurtzite structure-or a combination of both. 8 These two structures are so similar that a stacking fault in one structure can be locally regarded as a very small segment of the respective other structure. Within the zinc blende phase, altering the stacking sequence can give rise to a twin plane, representing a mirror plane between two stacking fault-free segments. 9 Among arsenic and phosphorus based nanowires, it is rather uncommon to find nanowires consisting of the pure zinc blende phase. Due to the low ionicity of InSb (f i = 0.19), the cubic zinc blende structure is much more stable (compared to arsenic and phosphorus based nanowires), and hence, the energy required to form a stacking fault and/or twin is substantial. For InSb the energy difference between the wurtzite and zinc blende structure was calculated to be 8.2 meV/atom. Only AlSb (9.5 meV/atom) and GaSb (9.9 meV/atom) show higher values. 10 This high energy difference favors the formation of stacking fault-free InSb nanowires, as will be demonstrated within this report.However, controlled epitaxial growth of InSb nanowires is challenging due to its huge lattice mismatch with respect to common semiconductor substrates such as Si (19%), GaAs (15%), or InAs (7%), although by the use of low temperature buffer layers thin film growth of InSb has been demonstrated. 11 Furthermore, due to the low melting point of InSb (T m = 525°C) in combination with the rather high decomposition temperature of common antimony precursors, 12 the temperature window for InSb growth is rather small. As yet, only few reports on controlled epitaxial InSb nanowire growth exist, 13À16 and notably, these works have in common that severe parasitic thin film growth was observed.Herein we report the synthesis of InSb nanowires grown on InSb(À1À1À1) B substrates using chemical beam epitaxy (CBE). CBE has some distinct advantages over other epitaxial growth techniques such as molecular beam epitaxy (MBE) and metalÀor-ganic vapor phase epitaxy (MOVPE). Compared to MBE, the growth rate is much higher and source control is easy due to the use of electronic mass flow controllers. In contrast to MOVPE, the accessible temperature window is significantly...

We report on the growth of GaSb nanotrees on InAs { ̅1 ̅1 ̅1}(B) substrates by chemical beam epitaxy. GaSb nanotrees form by the nucleation of Ga droplets on the surface of < ̅1 ̅1 ̅1>(B) oriented GaSb nanowires followed by the epitaxial growth of branches catalyzed by these Ga droplets. In the tip region, the trunks of the GaSb nanotrees are periodically twinned, which is attributed to a change of the effective V/III ratio at the later stage of growth as a consequence of the change in surface structure. The reflectivity of a forest of nanotrees was measured for a broad spectral range and compared to the reflectivity of a GaSb ( ̅1 ̅1 ̅1)(B) wafer and of GaSb nanowires. At wavelengths from 500 to 1700 nm, the presence of GaSb nanotrees decreased the reflection by three orders of magnitude compared to a blank GaSb substrate.

ZnO can appear as nanowires, nanobelts, and nanocombs, which are attractive for various applications. However, this has prevented the growth of desired nanostructures without other trace morphologies. Here we demonstrated a mechanism for selective growth of pure and long ZnO nanowires. This was obtained by placing a gold film at a high-temperature zone so that ZnO nanowires with controllable densities can be grown on adjacent bare substrates at lower temperature zones. The concentration gradients of gold and ZnO vapors are responsible for this selective growth, which could be applicable for selective growth of ZnO nanobelts and nanocombs in the future.