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25 Aug 2008

Volume 93, Issue 8, Articles (08xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 93, 083901 (2008); http://dx.doi.org/10.1063/1.2973167 (3 pages)

R. J. Martín-Palma, C. G. Pantano, and A. Lakhtakia
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High-density one-dimensional well-aligned germanium quantum dots on a nanoridge array

Yan-Ru Chen, Chieh-Hsiung Kuan, Yuen-Wuu Suen, Yu-Hwa Peng, Peng-Shiu Chen, Cha-Hsin Chao, Eih-Zhe Liang, Ching-Fuh Lin, and Hung-Chun Lo

Appl. Phys. Lett. 93, 083101 (2008); http://dx.doi.org/10.1063/1.2976549 (3 pages) | Cited 3 times

Online Publication Date: 26 August 2008

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The selective growth of high-density one-dimensional well-aligned Ge quantum dots (QDs) on the top of nanoridges patterned on Si substrate is reported. The period of ridge array is 150 nm, the width of each ridge is 80 nm, and the depth of the trench is 20 nm. The areal density of QDs is about 5.4×109 cm−2. Simulations of the chemical potential show that a proper distribution of the surface curvature may give rise to a suitable chemical potential minimum helping positioning the QDs. These ridges can also be used to control the shape and the uniformity of QDs.
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81.07.Ta Quantum dots
81.16.Dn Self-assembly
65.80.-g Thermal properties of small particles, nanocrystals, nanotubes, and other related systems

Ultrafast dynamics of photoexcited charge carriers in nanocrystalline diamond

P. Němec, J. Preclíková, A. Kromka, B. Rezek, F. Trojánek, and P. Malý

Appl. Phys. Lett. 93, 083102 (2008); http://dx.doi.org/10.1063/1.2970962 (3 pages) | Cited 3 times

Online Publication Date: 26 August 2008

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We report on ultrafast charge carrier dynamics in sub-band-gap energy states in nanocrystalline diamond self-supporting membranes prepared by plasma-enhanced chemical vapor deposition technique. The obtained data are hence not influenced by the substrate effects. Results of the femtosecond transient transmission and photoluminescence laser spectroscopy indicate relaxation of photoexcited carriers with the time constants of the order of 1 ps. This is attributed to an ultrafast spatial separation of holes and electrons at the surface of nanocrystals. Only the carrier population photoexcited in energy levels of 1.68 eV silicon related center decays on a much longer time scale with the time constant of 2.4 ns.
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73.63.Bd Nanocrystalline materials
78.67.Bf Nanocrystals, nanoparticles, and nanoclusters
78.47.J- Ultrafast spectroscopy (<1 psec)
78.55.Ap Elemental semiconductors
73.61.Cw Elemental semiconductors
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths

Structural properties of GaAsN/GaAs quantum wells studied at the atomic scale by cross-sectional scanning tunneling microscopy

J. M. Ulloa, P. M. Koenraad, and M. Hopkinson

Appl. Phys. Lett. 93, 083103 (2008); http://dx.doi.org/10.1063/1.2968213 (3 pages) | Cited 4 times

Online Publication Date: 26 August 2008

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The nitrogen distribution in GaAsN/GaAs quantum wells (QWs) grown by molecular beam epitaxy is studied on the atomic scale by cross-sectional scanning tunneling microscopy. No nitrogen clustering is observed in the range of N contents studied (between 1.0% and 2.5%, as measured by counting the individual N atoms inside the QW). Nevertheless, the upper interface roughness increases with the amount of N. A residual N concentration in the GaAs barriers is found, which strongly increases with the amount of N in the QW.
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68.65.Fg Quantum wells
71.55.Eq III-V semiconductors
68.35.Ct Interface structure and roughness

Low-loss left-handed metamaterials at millimeter waves

Fuli Zhang, Davy P. Gaillot, Charles Croënne, Eric Lheurette, Xavier Mélique, and Didier Lippens

Appl. Phys. Lett. 93, 083104 (2008); http://dx.doi.org/10.1063/1.2975187 (3 pages) | Cited 4 times

Online Publication Date: 26 August 2008

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An omega-type multilayered metamaterial aimed at operating at millimeter wavelengths was characterized between 75 and 110 GHz (W-band). The fabrication involves a monolithic integration of planar arrays of broad-side coupled microresonators with a benzocyclobutene spacing layer printed onto quartz substrates. The frequency dependence of the transmittance shows a well-resolved transmission window centered around 80 GHz with a 10% fractional bandwidth and another one starting from 100 GHz, both displaying comparable high transmission levels. The left- or right-handed behavior is assessed by the comparison of the phase delay between two devices of different lengths and by tilted-incidence transmission experiments.
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42.70.-a Optical materials
78.67.Pt Multilayers; superlattices; photonic structures; metamaterials
78.70.Gq Microwave and radio-frequency interactions

Influence of interface roughness on the performance of nanoparticulate zinc oxide field-effect transistors

Koshi Okamura, Norman Mechau, Donna Nikolova, and Horst Hahn

Appl. Phys. Lett. 93, 083105 (2008); http://dx.doi.org/10.1063/1.2972121 (3 pages) | Cited 25 times

Online Publication Date: 26 August 2008

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Nanoparticulate zinc oxide is regarded as one of the most promising inorganic materials for printable field-effect transistors (FETs), which work in the n-channel enhancement mode, due to the compatibility with solution, low-temperature, and high throughput processes. Since nanoparticulate films are composed of the nanoparticles and their agglomerates, the roughness of the interface to the insulating layer, where the channel of the FETs is formed, is a critical issue. Thus, the influence of the interface roughness on the field-effect mobility of the FETs is investigated in conjunction with film roughness and capacitance analyses. The field-effect mobility increases almost by a factor of 50, from 2.0×10−4 to 8.4×10−3 cm2 V−1 s−1, even if the reduction in the average roughness of the films is as small as 1.7 nm.
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85.30.Tv Field effect devices

Direct observation of the size dependence of Dexter energy transfer from polymer to small PbS quantum dots

Yating Zhang and Zhangcheng Xu

Appl. Phys. Lett. 93, 083106 (2008); http://dx.doi.org/10.1063/1.2975847 (3 pages) | Cited 5 times

Online Publication Date: 26 August 2008

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Small PbS quantum dots (QDs) with diameters ranging from 2.5 to 3 nm were synthesized directly in the conjugated polymer poly[2-methoxy-5-(2′-ethyl-hexyloxy)-p-phenylene vinylene] (MEH-PPV) at 70 °C. To monitor the size dependence of Dexter energy transfer [ D. L. Dexter, J. Chem. Phys. 21, 836 (1953) ] from MEH-PPV to PbS QDs, the photoluminescence of MEH-PPV is measured for a series of samples with varying QD sizes controlled by the reaction time. A decreased transfer rate is observed for PbS QDs with a diameter of about 2.65 nm due to the minimum overlap between the emission spectrum of MEH-PPV and the 1Se-1Sh and 1Pe-1Sh transitions of PbS QDs.
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78.67.Hc Quantum dots
82.35.Np Nanoparticles in polymers
81.16.-c Methods of micro- and nanofabrication and processing

Effect of defects on oscillation characteristics and instability of carbon nanotube-based oscillators

P. Liu, H. J. Gao, and Y. W. Zhang

Appl. Phys. Lett. 93, 083107 (2008); http://dx.doi.org/10.1063/1.2976127 (3 pages) | Cited 13 times

Online Publication Date: 26 August 2008

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The oscillatory characteristics and the instability of double- and triple-walled carbon nanotube-based oscillators containing a vacancy or a Stone–Wales (SW) defect were investigated by molecular dynamics simulations. It was found that the existence of these defects markedly affects the oscillation period and amplitude. The defect-free oscillators are most stable, followed by oscillators containing a SW defect, while oscillators containing a vacancy are least stable. The origin of the defect-induced instability is due to the change in potential energy profile and the resulting force fluctuation.
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61.48.De Structure of carbon nanotubes, boron nanotubes, and other related systems
62.25.-g Mechanical properties of nanoscale systems

Epitaxial nanotwinned Cu films with high strength and high conductivity

O. Anderoglu, A. Misra, H. Wang, F. Ronning, M. F. Hundley, and X. Zhang

Appl. Phys. Lett. 93, 083108 (2008); http://dx.doi.org/10.1063/1.2969409 (3 pages) | Cited 31 times

Online Publication Date: 26 August 2008

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We report on the synthesis of epitaxial (single-crystal-like), nanotwinned Cu films via magnetron sputtering. Increasing the deposition rate from 1 to 4 nm/s decreased the average twin lamellae spacing from 16 to 7 nm. These epitaxial nanotwinned Cu films exhibit significantly higher ratio of hardness to room temperature electrical resistivity than columnar grain (nanocrystalline), textured, nanotwinned Cu films.
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81.05.Bx Metals, semimetals, and alloys
81.15.Cd Deposition by sputtering
68.55.at Other materials
73.61.At Metal and metallic alloys
81.40.Np Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure
62.20.Qp Friction, tribology, and hardness

Reversible work function changes induced by photoisomerization of asymmetric azobenzene dithiol self-assembled monolayers on gold

Lloyd F. N. Ah Qune, H. Akiyama, T. Nagahiro, K. Tamada, and Andrew T. S. Wee

Appl. Phys. Lett. 93, 083109 (2008); http://dx.doi.org/10.1063/1.2969468 (3 pages) | Cited 12 times

Online Publication Date: 26 August 2008

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We measured reversible changes in the work function (ΔϕAu) of gold substrates modified by asymmetric azobenzene dithiol self-assembled monolayers (SAMs) following photoisomerization and thermal recovery of the azo unit. The azobenzene derivative SAMs were photoisomerized to cis form by UV irradiation. ΔϕAu was monitored in real time during thermal recovery to trans form by ultraviolet photoelectron spectroscopy using a synchrotron light source. Changing the substituted functional group in the p′ position of the azobenzene from electron donating to electron withdrawing resulted in opposite responses of ΔϕAu against photoisomerization. Hence, a direct correlation between ΔϕAu and changes in molecular dipole moments was obtained.
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82.30.Qt Isomerization and rearrangement
73.30.+y Surface double layers, Schottky barriers, and work functions
82.80.Pv Electron spectroscopy (X-ray photoelectron (XPS), Auger electron spectroscopy (AES), etc.)
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
82.50.Hp Processes caused by visible and UV light
68.47.Pe Langmuir-Blodgett films on solids; polymers on surfaces; biological molecules on surfaces

Partially coherent extreme ultraviolet interference lithography for 16 nm patterning research

M. Goldstein, A. Wüest, and D. Barnhart

Appl. Phys. Lett. 93, 083110 (2008); http://dx.doi.org/10.1063/1.2973178 (3 pages) | Cited 4 times

Online Publication Date: 26 August 2008

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Conditions are reported under which a partially coherent plasma source of 13.5 nm wavelength radiation is found to be suitable for interference lithography. The predicted resolution exceeds the capability of present imaging systems and is comparable to synchrotron-based approaches. Methods borrowed from ray tracing are utilized for a partially coherent interference analysis, and a rigorous coupled wave theory is applied to optimize grating efficiency. The results suggest that a compact patterning tool with a resolution of 16 nm is possible by a careful selection of the design parameters.
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81.16.Nd Micro- and nanolithography
85.40.Hp Lithography, masks and pattern transfer

Strain-compensated InAs/GaNAs quantum dots for use in high-efficiency solar cells

Ryuji Oshima, Ayami Takata, and Yoshitaka Okada

Appl. Phys. Lett. 93, 083111 (2008); http://dx.doi.org/10.1063/1.2973398 (3 pages) | Cited 81 times

Online Publication Date: 26 August 2008

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We have investigated GaAs-based p-i-n quantum dot solar cells (QDSCs) with 10 up to 20 stacked layers of self-assembled InAs quantum dots (QDs) grown by atomic hydrogen-assisted molecular beam epitaxy. The net average lattice strain was minimized by using the strain-compensation technique, in which GaNAs dilute nitrides were used as spacer layers. The filtered short-circuit current density beyond GaAs bandedge was 2.47 mA/cm2 for strain-compensated QDSC with 20 stacks of InAs QD layers, which was four times higher than that for strained QDSC with identical cell structure.
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84.60.Jt Photoelectric conversion
68.65.Hb Quantum dots (patterned in quantum wells)
68.55.A- Nucleation and growth

Phonon backscattering and thermal conductivity suppression in sawtooth nanowires

Arden L. Moore, Sanjoy K. Saha, Ravi S. Prasher, and Li Shi

Appl. Phys. Lett. 93, 083112 (2008); http://dx.doi.org/10.1063/1.2970044 (3 pages) | Cited 28 times

Online Publication Date: 26 August 2008

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The effect of surface roughness on phonon transport in a nanowire has often been described by treating the surface as flat with a specularity parameter (p) in the range between 0 and 1. A lower thermal conductivity limit is approached at p = 0 for diffuse surface. It is demonstrated here by Monte Carlo simulation that sawtooth roughness on a nanowire can cause phonon backscattering and suppress the thermal conductivity below the diffuse surface limit. The backscattering effect can be accounted for only by a negative p if the detail of the surface roughness is ignored.
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63.22.Gh Nanotubes and nanowires
73.63.Bd Nanocrystalline materials
68.35.B- Structure of clean surfaces (and surface reconstruction)
66.70.-f Nonelectronic thermal conduction and heat-pulse propagation in solids; thermal waves

Direct electrical measurement of an individual α-Fe2O3 nanobridge field effect transistor formed via one-step thermal oxidation

Li-Chieh Hsu and Yuan-Yao Li

Appl. Phys. Lett. 93, 083113 (2008); http://dx.doi.org/10.1063/1.2976547 (3 pages) | Cited 3 times

Online Publication Date: 27 August 2008

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An α-Fe2O3 nanobridge (NB) was laterally grown via the one-step thermal oxidation of 150 nm Fe film at 350 °C for 1 h in air atmosphere to form a NB field effect transistor (FET). The diameter of the as-grown NB was 7 nm, with a length of 170 nm. The electrical properties of the individual α-Fe2O3 NB were directly measured by microprobing the NB FET. The results show that the NB demonstrated N-type semiconductive behavior with a conductivity of 1.67 S/cm.
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85.30.Tv Field effect devices
81.16.Pr Micro- and nano-oxidation

Dilution effects on the photoluminescence of ZnSe quantum-dot dispersions

Bing C. Mei, Jun Wang, Qi Qiu, Tracy Heckler, Athos Petrou, and T. J. Mountziaris

Appl. Phys. Lett. 93, 083114 (2008); http://dx.doi.org/10.1063/1.2970995 (3 pages) | Cited 6 times

Online Publication Date: 27 August 2008

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We report results for the photoluminescence emission intensity from ZnSe quantum-dot dispersions in liquids as a function of particle concentration. The observed emission intensity initially increases with dilution, exhibits a maximum, and then decreases. The optimal particle concentration yielding the maximum emission intensity increases as the particle size decreases. The corresponding optimal interparticle distance was estimated for three quantum-dot populations having different average particle size. The observed behavior depends on fundamental physical interactions between the exciting and emitted radiation and the quantum dots; it is expected to be valid for any quantum-dot dispersion, irrespective of material type.
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78.55.Et II-VI semiconductors
78.67.Hc Quantum dots

Electronic and transport properties of contacts between molybdenum sulfide nanowires and gold electrodes

Igor Popov, Alessandro Pecchia, Shinya Okano, Nitesh Ranjan, Aldo Di Carlo, and Gotthard Seifert

Appl. Phys. Lett. 93, 083115 (2008); http://dx.doi.org/10.1063/1.2976680 (3 pages) | Cited 1 time

Online Publication Date: 27 August 2008

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We report unique electronic and transport properties of contacts between a molybdenum sulfide nanowire and a gold electrode. The pointlike contacts exhibit a remarkable transparency for the charge carrier injection, which is the consequence of the “task division” between sulfur and molybdenum atoms at the interface with the gold electrode, where sulfur binds the nanowire to the electrode, and the current flows unperturbed through the direct Au–Mo channels. The unique properties of the analyzed contacts solve some major drawbacks in the molecular electronics devices, such as the difficulties for the current injection from the electrodes into conjugated carbon-based molecules.
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73.40.Ns Metal-nonmetal contacts
73.63.Nm Quantum wires
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
72.80.Jc Other crystalline inorganic semiconductors

Visualization of weak confinement potentials by near-field optical imaging spectroscopy of exciton and biexciton in a single quantum dot

Y. Sugimoto, T. Saiki, and S. Nomura

Appl. Phys. Lett. 93, 083116 (2008); http://dx.doi.org/10.1063/1.2976145 (3 pages) | Cited 7 times

Online Publication Date: 27 August 2008

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Imaging spectroscopy of a single GaAs interface fluctuation quantum dot (IFQD) was performed using a near-field scanning optical microscope (NSOM) with a spatial resolution of 40 nm. A difference in the emission profiles of an exciton and a biexciton was found for several IFQDs. By comparing with a numerical simulation based on the finite-difference time-domain method, this difference was attributed to the existence of a shallow potential dip in the IFQD. The NSOM wavefunction mapping for excitons and biexcitons as quasiparticles with different masses is a tool for investigating weak confinement potentials to detect local strain and disorder.
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73.21.La Quantum dots
71.35.-y Excitons and related phenomena

Room temperature luminescent InGaAs/GaAs core-shell nanowires

F. Jabeen, S Rubini, V Grillo, L. Felisari, and F. Martelli

Appl. Phys. Lett. 93, 083117 (2008); http://dx.doi.org/10.1063/1.2977475 (3 pages) | Cited 14 times

Online Publication Date: 28 August 2008

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InGaAs/GaAs core-shell nanowires have been grown by molecular beam epitaxy. The core-shell nanowires show room temperature photoluminescence. At low temperatures their luminescence intensity is two to three orders of magnitudes larger than that of parent InGaAs nanowires grown without external GaAs shell. The nanowires have been structurally characterized by scanning electron microscopy and transmission electron microscopy.
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78.67.Lt Quantum wires
78.55.Cr III-V semiconductors
68.65.La Quantum wires (patterned in quantum wells)
61.46.Km Structure of nanowires and nanorods (long, free or loosely attached, quantum wires and quantum rods, but not gate-isolated embedded quantum wires)

Bandgap bowing in BGaN thin films

A. Ougazzaden, S. Gautier, T. Moudakir, Z. Djebbour, Z. Lochner, S. Choi, H. J. Kim, J.-H. Ryou, R. D. Dupuis, and A. A. Sirenko

Appl. Phys. Lett. 93, 083118 (2008); http://dx.doi.org/10.1063/1.2977588 (3 pages) | Cited 4 times

Online Publication Date: 28 August 2008

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We report on the bandgap variation in thin films of BxGa1−xN grown on AlN/sapphire substrates using metal-organic vapor phase epitaxy. Optical transmission, photoluminescence, and x-ray diffraction were utilized to characterize the materials’ properties of the BxGa1−xN films. In contrast to the common expectation for the bandgap variation, which is based on the linear interpolation between the corresponding GaN and BN values, a significant bowing (C = 9.2±0.5 eV) of the bandgap was observed. A decrease in the optical bandgap by 150 meV with respect to that of GaN was measured for the increase in the boron composition from 0% to 1.8%.
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78.66.Fd III-V semiconductors
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
68.55.ag Semiconductors
81.15.Kk Vapor phase epitaxy; growth from vapor phase
78.55.Cr III-V semiconductors

rf resistance and inductance of massively parallel single walled carbon nanotubes: Direct, broadband measurements and near perfect 50 Ω impedance matching

Chris Rutherglen, Dheeraj Jain, and Peter Burke

Appl. Phys. Lett. 93, 083119 (2008); http://dx.doi.org/10.1063/1.2970031 (3 pages) | Cited 19 times

Online Publication Date: 28 August 2008

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We report using dielectrophoresis to accumulate hundred to thousands of solubilized single walled carbon nanotubes in parallel to achieve impedance values very close to 50 Ω. This allows us to clearly measure the real (resistive) and imaginary (inductive) impedance over a broad frequency range. We find a negligible to mild frequency dependent resistance for the devices and an imaginary impedance that is significantly smaller then the resistance over the range of dc to 20 GHz. This clearly and unambiguously demonstrates that kinetic inductance is not the major issue facing nanotube array interconnects, when compared to the real impedance (the resistance).
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73.63.Fg Nanotubes
82.45.Yz Nanostructured materials in electrochemistry

Reversible separation of single-walled carbon nanotubes in bundles

Sangeeta Sahoo, Ravi Maranganti, Sarah Lastella, Govind Mallick, Shashi Karna, Pradeep Sharma, and Pulickel M. Ajayan

Appl. Phys. Lett. 93, 083120 (2008); http://dx.doi.org/10.1063/1.2976631 (3 pages)

Online Publication Date: 29 August 2008

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We show that electrostatic charging of nanotubes and the consequent repulsion can lead to reversible separation of individual single-walled carbon nanotubes in bundles. Low-energy electron beam irradiation leads to this completely reversible phenomenon. A simple semianalytical model is used to explain the observed separation mechanism. The reversibility of the separation process is attributed to discharging and thermal-fluctuation induced motion of the nanotubes in ambient air. Further, the separation impacts the electrical conductance of small nanotube bundled devices.
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73.63.Fg Nanotubes
61.82.Rx Nanocrystalline materials
61.48.De Structure of carbon nanotubes, boron nanotubes, and other related systems
85.35.Kt Nanotube devices

High-bias breakdown of Au/1,4-benzenedithiol/Au junctions

Yumi Teramae, Kazunori Horiguchi, Shuhei Hashimoto, Makusu Tsutsui, Shu Kurokawa, and Akira Sakai

Appl. Phys. Lett. 93, 083121 (2008); http://dx.doi.org/10.1063/1.2976666 (3 pages) | Cited 7 times

Online Publication Date: 29 August 2008

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We have studied the high-bias breakdown of Au/1,4-benzenedithiol (BDT)/Au junctions at room temperature. Exploiting the break junction technique, we held a Au/BDT/Au junction and ruptured it by applying a voltage ramp. The conductance first changes gradually with the bias and then abruptly increases at breakdown. We found that the breakdown voltage shows a broad distribution and takes a maximum at ∼ (1.2–1.5)V. The breakdown voltage is unaffected by the ambient atmosphere but tends to slightly decrease with increasing the junction conductance. We consider that the Au electrode becomes unstable at the breakdown voltage and collapses to crush the junction.
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73.40.Ns Metal-nonmetal contacts

Visualization of nanoscale peeling of carbon nanotube on graphite

Makoto Ishikawa, Ryuichi Harada, Naruo Sasaki, and Kouji Miura

Appl. Phys. Lett. 93, 083122 (2008); http://dx.doi.org/10.1063/1.2959188 (3 pages) | Cited 11 times

Online Publication Date: 29 August 2008

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We have fabricated a manipulation system with a force detection, which uses a self-detective cantilever, in a chamber of a scanning electron microscope. This system can simultaneously manipulate a nanoparticle and detect a force needed to move it, a detective resolution of which is approximately 1 nN. In this work, nanoscale peeling processes of a multiwalled carbon nanotube (MWCNT) on the graphite substrate have been studied. We have first experimentally obtained the vertical force-distance curve with the characteristic hysteresis loop which exhibits the multistable states between line contact and point contact of the MWCNT shape during the peeling processes.
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81.07.De Nanotubes

Sub-30-nm patterning on quartz for imprint lithography templates

Charan Srinivasan, J. Nathan Hohman, Mary E. Anderson, Paul S. Weiss, and Mark W. Horn

Appl. Phys. Lett. 93, 083123 (2008); http://dx.doi.org/10.1063/1.2963982 (3 pages) | Cited 6 times

Online Publication Date: 29 August 2008

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A parallel and economical method for obtaining nanoscale features on large-area quartz substrates has been developed for use in nanoimprint lithography template fabrication. Self-assembled multilayer films (molecular rulers) are used in conjunction with photolithographically defined metallic features to generate precise nanogaps with sub-30-nm resolution on quartz substrates. These nanopatterns are then transferred to the quartz substrates using the metallic thin films as etch masks.
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81.16.Nd Micro- and nanolithography
81.16.Rf Micro- and nanoscale pattern formation
81.16.Dn Self-assembly
81.65.Cf Surface cleaning, etching, patterning

Fabrication of zinc oxide nanorods based heterojunction devices using simple and economic chemical solution method

N. Koteeswara Reddy, Q. Ahsanulhaq, and Y. B. Hahn

Appl. Phys. Lett. 93, 083124 (2008); http://dx.doi.org/10.1063/1.2975829 (3 pages) | Cited 15 times

Online Publication Date: 29 August 2008

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In this letter we reported the behavior of zinc oxide nanorods/gallium nitride (ZnO/GaN) heterojunctions at different temperatures. The well-aligned ZnO nanorods were synthesized on GaN coated alumina (Al2O3) substrate using a solution method at lower temperatures. The as-grown p-n junction diode exhibited a low turn-on voltage of ∼ 0.65 V with an excellent rectifying behavior. While increasing temperature, the series resistance of the device slightly increased due to the formation of metallic bonds between metal and semiconductor. These results, therefore, emphasize that the as-grown heterostructures are quite stable even at higher temperatures.
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85.30.Kk Junction diodes
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