This paper summarizes some of the essential aspects of silicon‐nanowire growth and of their electrical properties. In the first part, a brief description of the different growth techniques is given, though the general focus of this work is on chemical vapor deposition of silicon nanowires. The advantages and disadvantages of the different catalyst materials for silicon‐wire growth are discussed at length. Thereafter, in the second part, three thermodynamic aspects of silicon‐wire growth via the vapor–liquid–solid mechanism are presented and discussed. These are the expansion of the base of epitaxially grown Si wires, a stability criterion regarding the surface tension of the catalyst droplet, and the consequences of the Gibbs–Thomson effect for the silicon wire growth velocity. The third part is dedicated to the electrical properties of silicon nanowires. First, different silicon nanowire doping techniques are discussed. Attention is then focused on the diameter dependence of dopant ionization and the influence of interface trap states on the charge carrier density in silicon nanowires. It is concluded by a section on charge carrier mobility and mobility measurements.

Volker Schmidt studied Physics at the Bayerische Julius-Maximilians-Universita ¨t Wu ¨rzburg, Germany, and at the State University of New York at Buffalo. He received his Ph.D. from the Max Planck Institute of Microstructure Physics in Halle, Germany, working on growth and properties of silicon nanowires. Volker Schmidt also worked as a guest scientist at the IBM Zurich research laboratories in Ru ¨schlikon, Switzerland,

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.

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...