Growth rate of a crystal facet of arbitrary size and growth kinetics of vertical nanowires

Dubrovskiı̆, V. G.; Sibirev, N. V.

doi:10.1103/physreve.70.031604

Cited by 117 publications

(114 citation statements)

References 16 publications

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“…For instance, Akiyama et al calculated a critical radius of 5.6 nm for GaAs NWs. These approaches have in common to treat the energetics of fully formed NWs and to predict critical radii far too small to explain the occurrence of WZ in NWs with radii up to at least 100 nm.On the other hand, from the very beginnings of VLS studies, it has been argued that the two-dimensional (2D) nucleation of new solid layers from the supersaturated liquid was of paramount importance [14] and most theories of NW growth take nucleation into account [15,16,17]. The fact that the faults in each phase and those separating ZB and WZ regions are perpendicular to the growth axis, in other words that each monolayer (ML) of III-V pairs is uniform in structure and orientation, strongly suggests that, once a nucleus of critical size is formed, it rapidly spreads out laterally over the whole solid/liquid (SL) interface [5,11], unless the wire is very wide .…”

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confidence: 99%

Why Does Wurtzite Form in Nanowires of III-V Zinc Blende Semiconductors?

2007

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We develop a nucleation-based model to explain the formation of the wurtzite (WZ) phase during the vapor-liquid-solid growth of free-standing nanowires of zinc-blende (ZB) semiconductors. Nucleation occurs preferentially at the edge of the solid/liquid interface, which entails major differences between ZB and WZ nuclei. Depending on the pertinent interface energies, WZ nucleation is favored at high liquid supersaturation. This explains our systematic observation of ZB during early growth.PACS numbers: 68.65. La,64.60.Qb,81.05.Ea,81.15.Kk,64.70.Nd Free-standing wires with diameters ranging from hundreds down to a few nanometers are nowadays commonly fabricated from a large range of semiconductor materials [1,2,3,4,5]. These nanowires (NWs) have remarkable physical properties and many potential applications. The present work deals with the epitaxial growth of NWs of III-V semiconductors on a hot substrate. Metal catalyst nanoparticles deposited on the substrate before growth define the wire diameter. According to the vapor-liquidsolid (VLS) growth mechanism, the atoms are fed from the vapor phase to the solid wire through this particle (or droplet), which remains liquid during growth [6].We consider III-V compounds which, under bulk form, adopt the cubic zinc-blende (ZB) crystal structure [7] (although some non-ZB high-pressure phases [8] may be metastable at atmospheric pressure [9]), leaving aside nitrogen-based NWs. We discuss the usual case of NWs grown on a [111]B (As-terminated) face of the ZB substrate. Probably the most surprising feature of these NWs is that, in contrast to their bulk counterparts, they often adopt the hexagonal wurtzite (WZ) structure. This was observed for most ZB III-V materials and growth techniques [1,3,4,10,11]. However, although often dominantly of WZ structure, the NWs usually contain stacking faults (SFs) and sequences of ZB structure. The coexistence of two phases is clearly a problem for basic studies as well as applications, so that phase purity control is one of the main challenges of III-V NW fabrication.The surprising prevalence of the WZ structure in III-V NWs has not been explained satisfactorily so far. Here, based on new experimental observations, we propose an explanation of the occurrence of the WZ structure and develop a model predicting quantitatively in which growth conditions it should form. We consider the specific case of gold-catalyzed GaAs NWs grown by molecular beam epitaxy (MBE) on a GaAs substrate but we expect our model and our conclusions to remain valid for any ZB III-V compound and any growth method.Let us start with briefly reviewing previously proposed explanations. Calculations give the difference δw in cohesive energy between ZB and WZ bulk GaAs as about 24 meV per III-V pair at zero pressure [7]. It has been argued that this favoring of the ZB form might be offset in NWs of small diameter by the large relative contribution to the total energy of either the lateral facets [12] or the vertical edges separating the latter [13] (provided the specifi...

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Why Does Wurtzite Form in Nanowires of III-V Zinc Blende Semiconductors?

2007

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“…17 Recently, within a nucleation mediated growth scenario, both linear and quadratic dependences of nanowire growth rates on Δμ have been reported. 18,[26][27][28] Accordingly, altering the supersaturation will readily influence the growth behavior of nanowires, favoring faster crystallization rates at high Δμ values. Directly influencing Δμ to manipulate the growth rate of nanowires has previously been achieved by altering the partial pressure of the vapor source, 29 according to…”

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Manipulating the Growth Kinetics of Vapor–Liquid–Solid Propagated Ge Nanowires

et al. 2013

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“…The use of a low-temperature NiO catalyst (at the same pressures and flow velocities of argon and target-substrate distances) makes it possible to reduce the growth temperature to 570°C . The minimum radius of a growing nanowire decreases (at a constant gas flow), approximately inversely proportionally to the growth temperature [8]. HRTEM analysis showed that ZnO nanowires in the ZnO/NiO/GaN/Si(111) structure are completely free of dislocations and have a perfect internal structure (Fig.…”

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Structure and optical properties of ZnO nanowires fabricated by pulsed laser deposition on GaN/Si(111) films with the use of Au and NiO catalysts

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Lorenz

Lenzner

et al. 2008

Bull. Russ. Acad. Sci. Phys.

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-The growth of ZnO nanowires on a Si(111) substrate with a GaN buffer layer by pulsed laser deposition at a high argon pressure and with the use of Au and NiO catalysts has been investigated. Application of the low-temperature NiO catalyst makes it possible to reduce the optimal growth temperature from 900 ° C (in the case of the Au catalyst) to T = 570°C and grow ZnO nanowires 20 nm in diameter, which are highly-oriented in the direction of the c lattice axis and completely free of dislocations. DOI: 10.3103/S1062873808080315A promising direction in nanotechnology is the development of methods of self-assembled growth of semiconductor nanowires. The combination of high optical, mechanical, and piezoelectric properties of ZnO determines good prospects of this material in design of new nanoelectronic devices.Hybrid structures based on ZnO nanowires and films that are highly-oriented along the c axis are promising as basic elements of UV ZnO nanolasers with optical, electrical, and electron-beam pumping, UV photodetectors, nanotransistors, electron emitters, piezoelectric nanocomposites with a dielectric or polymer filling, piezoelectric transducers and acoustic receivers, high-efficiency solar energy converters, nanosensors of chemical and biological materials, and elements of devices for nanomechanics and nanospintronics.Despite significant efforts, p -ZnO structures with high mobility have not yet been obtained. Therefore, it was proposed in [1] to use n-ZnO/ p -GaN for heterojunctions to fabricate light-emitting ZnO-based film structures. The first light-emitting heterostructure of the n -ZnO nanowire/epitaxial p-GaN film type was investigated in [2]. However, the low electroluminescence intensity in the UV region and high-intensity green luminescence indicated poor structural quality of the nanostructures obtained.We investigated the growth of ZnO nanowires on an n -GaN epitaxial film formed on a (111)Si substrate by organometallic vapor deposition. ZnO nanowires were fabricated by pulsed laser deposition [3][4][5][6] in an evacuated quartz cell using an external resistive heater. Radiation of a KrF laser ( λ = 248 nm) was focused on the surface of a rotating ZnO ceramic target. The energy density in a pulse on the target surface was 2 J cm -2 . The laser pulse repetition rate was 3-10 Hz. Synthesis of ZnO nanowires was performed applying from 12 to 24 thousand laser pulses. The substrate temperature was varied in the range 850-950°C . The quartz cell was previously evacuated to a pressure of 5 Pa. Then highpurity (99.998%) argon was leeked into the chamber. The argon flow was 0.2 l min -1 at a pressure of 75-200 mbar. Si(111) substrates with previously deposited epitaxial GaN films were oriented parallel to the laser torch at a distance of 20-35 mm from the target surface. A thin gold layer ( h = 2-3 nm), used as a catalyst, was deposited on the substrate by rf magnetron sputtering.As our experiments showed, at temperatures from 900 to 1100 °C , an Au film with a thickness of 3-5 nm is divided into ...

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Growth rate of a crystal facet of arbitrary size and growth kinetics of vertical nanowires

Cited by 117 publications

References 16 publications

Why Does Wurtzite Form in Nanowires of III-V Zinc Blende Semiconductors?

Why Does Wurtzite Form in Nanowires of III-V Zinc Blende Semiconductors?

Manipulating the Growth Kinetics of Vapor–Liquid–Solid Propagated Ge Nanowires

Structure and optical properties of ZnO nanowires fabricated by pulsed laser deposition on GaN/Si(111) films with the use of Au and NiO catalysts

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