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1 Aug 2011

Volume 99, Issue 5, Articles (05xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 99, 051112 (2011); http://dx.doi.org/10.1063/1.3617421 (3 pages)

Wei Li, Jun Chen, Gerard Nouet, Liang-yao Chen, and Xunya Jiang
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Non-contact and all-electrical method for monitoring the motion of semiconducting nanowires

S. W. Hoch, J. R. Montague, V. M. Bright, C. T. Rogers, K. A. Bertness, J. D. Teufel, and K. W. Lehnert

Appl. Phys. Lett. 99, 053101 (2011); http://dx.doi.org/10.1063/1.3614562 (3 pages) | Cited 1 time

Online Publication Date: 1 August 2011

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The authors demonstrate an all-electric, non-contact method of monitoring the motion of semiconducting nanowires. This technique uses a microwave resonant circuit whose resonance is modulated by the varying capacitance between GaN nanowires and a metal tip. They estimate that the method is capable of detecting motion with a sensitivity of 1pm/math. They verify their technique by driving a nanowire and comparing the electrical signal to the nanowire motion determined from a scanning electron microscope image. Finally, they use this technique to measure the pressure dependence of a nanowire’s mechanical damping to be 8.37(0.08) Hz/Pa in the molecular flow regime.
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81.07.Gf Nanowires
81.05.Ea III-V semiconductors
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
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)

Patterning of silver nanoparticles on visible light-sensitive Mn-doped lithium niobate photogalvanic crystals

Xiaoyan Liu, Hideki Hatano, Shunji Takekawa, Fumio Ohuchi, and Kenji Kitamura

Appl. Phys. Lett. 99, 053102 (2011); http://dx.doi.org/10.1063/1.3622654 (3 pages) | Cited 2 times

Online Publication Date: 1 August 2011

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Visible light-induced polarization-dependent photochemical deposition of silver nanoparticles (AgNPs) has been demonstrated using Mn-doped congruent LiNbO3 (CLN) single crystals. Mn-doped CLN has a strong absorption over a wide region of the visible spectrum that allowed effective visible light irradiation for photochemical deposition. The AgNPs deposition on Mn-doped CLN was compared with that on non-doped congruent LiNbO3, and together these further confirmed that the photochemical deposition on LiNbO3 is caused by the strong photogalvanic effect.
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81.05.Bx Metals, semimetals, and alloys
81.07.Bc Nanocrystalline materials
81.16.Rf Micro- and nanoscale pattern formation
78.56.-a Photoconduction and photovoltaic effects
78.40.Kc Metals, semimetals, and alloys
78.67.Bf Nanocrystals, nanoparticles, and nanoclusters

Transparent interconnections formed by rapid single-step fabrication of graphene patterns

J. B. Park, W. Xiong, Z. Q. Xie, Y. Gao, M. Qian, M. Mitchell, M. Mahjouri-Samani, Y. S. Zhou, L. Jiang, and Y. F. Lu

Appl. Phys. Lett. 99, 053103 (2011); http://dx.doi.org/10.1063/1.3622660 (3 pages) | Cited 2 times

Online Publication Date: 1 August 2011

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We developed a process to form transparent interconnections using graphene patterns that were synthesized by laser chemical vapor deposition. The number of graphene layers was tightly controlled by laser scan speed. Graphene patterns were fabricated at a high scan speed of up to 200 μm/s with a single-step process. The process time is about a million times faster than the conventional chemical vapor deposition method. The fabricated graphene patterns on nickel foils were directly transferred to desired positions on patterned electrodes. The position-controlled transfer with rapid single-step fabrication of graphene patterns provides an innovative pathway for graphene-based interconnections.
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81.05.ue Graphene
81.05.Cy Elemental semiconductors
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.16.Mk Laser-assisted deposition
81.16.Rf Micro- and nanoscale pattern formation
85.40.Hp Lithography, masks and pattern transfer

Identification of embedded charge defects in suspended silicon nanowires using a carbon-nanotube cantilever gate

Yann-Wen Lan, Linh-Nam Nguyen, Shui-Jin Lai, Ming-Chou Lin, Chieh-Hsiung Kuan, and Chii-Dong Chen

Appl. Phys. Lett. 99, 053104 (2011); http://dx.doi.org/10.1063/1.3619177 (3 pages) | Cited 2 times

Online Publication Date: 1 August 2011

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A movable carbon nanotube (CNT) cantilever gate is developed for the detection of embedded charge defects in suspended nanowires. The CNT gate is composed of a gold probe welded to a thick CNT, which is in turn attached to a thinner CNT. The rigid welding of the thicker CNT to the gold probe allows for precise placement along the measured nanowire while the joint between the thinner and thicker CNT absorbs the push and pull forces of repeated relocation. For demonstration purpose, the CNT gate determines the site of the embedded charges and measures the amount of trapped electrons.
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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)
61.48.De Structure of carbon nanotubes, boron nanotubes, and other related systems
61.72.-y Defects and impurities in crystals; microstructure
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Origin of the n-type transport behavior of azafullerene encapsulated single-walled carbon nanotubes

Nguyen Thanh Cuong, Minoru Otani, Yoko Iizumi, Toshiya Okazaki, Georgios Rotas, Nikos Tagmatarchis, Yongfeng Li, Toshiro Kaneko, Rikizo Hatakeyama, and Susumu Okada

Appl. Phys. Lett. 99, 053105 (2011); http://dx.doi.org/10.1063/1.3619828 (3 pages) | Cited 2 times

Online Publication Date: 1 August 2011

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The transport properties of C59N encapsulated semiconducting single-walled carbon nanotubes (SWCNTs) (C59N-peapod) are investigated. Transport measurements of the peapods in field effect transistors (FETs) reveal that ∼14% of the C59N-peapod sample shows n-type behavior even though the electronic properties of the host SWCNTs are similar to those of C60-peapods that exhibit only p-type property. First-principles electronic-structure calculations reveal that the unique transport behavior originates from the monomer form of C59N encapsulated in SWCNTs. The singly occupied (SO) state of C59N lies in the energy gap of the SWCNT and the energy of this state increases substantially when electrons are injected. Because of this shift to higher energy, the SO state acts as a shallow donor state for the conduction band of the nanotube, which leads to n-type behavior in FET measurements.
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73.23.-b Electronic transport in mesoscopic systems
85.30.Tv Field effect devices
71.15.Mb Density functional theory, local density approximation, gradient and other corrections
71.20.Tx Fullerenes and related materials; intercalation compounds
73.20.At Surface states, band structure, electron density of states

Measuring the short-range force field above a single molecule with atomic resolution

Fabian Mohn, Leo Gross, and Gerhard Meyer

Appl. Phys. Lett. 99, 053106 (2011); http://dx.doi.org/10.1063/1.3619829 (3 pages) | Cited 10 times

Online Publication Date: 2 August 2011

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We present a method that enables atomic-resolution measurements of the short-range force field above a single organic admolecule using noncontact atomic force microscopy. We have extended the standard force-mapping technique to be able to measure at close tip–molecule distances, in regions that cannot be accessed by normal constant-height or constant-frequency-shift imaging. Our technique can be used to study the interaction between a well-defined scanning probe tip and an admolecule on the atomic scale and yields atomic resolution of both molecule and substrate. Furthermore, it enables the measurement of constant-frequency-shift topographies of molecules with nonplanar adsorption geometries.
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68.43.Mn Adsorption kinetics

The reproducibility of transport conditions at metal nanoparticle-semiconductor interfaces over a range of loading conditions

R. A. Kraya

Appl. Phys. Lett. 99, 053107 (2011); http://dx.doi.org/10.1063/1.3622634 (3 pages) | Cited 3 times

Online Publication Date: 3 August 2011

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Nanomaterials will serve as the foundation of future electronics, greatly improving efficiency and capabilities due to enhanced control of interfaces at the nanoscale. In this letter, the effect of various loading conditions on the transport characteristics of Au nanoparticle–SrTiO3 interfaces is investigated with an atomic force microscope in order to understand the effect and thus sensitivity of the interface to external stimuli. Two types of interfaces are identified—one robust against applied load and the other affected by small variations in load with improved performance with increased applied load.
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73.40.Ns Metal-nonmetal contacts
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Molecular dynamics simulations of oxide memristors: Crystal field effects

S. E. Savel’ev, A. S. Alexandrov, A. M. Bratkovsky, and R. Stanley Williams

Appl. Phys. Lett. 99, 053108 (2011); http://dx.doi.org/10.1063/1.3622665 (3 pages) | Cited 2 times

Online Publication Date: 3 August 2011

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We present molecular-dynamic simulations of memory resistors (memristors) including the crystal field effects on mobile ionic species such as oxygen vacancies appearing during operation of the device. Vacancy distributions show different patterns depending on the ratio of a spatial period of the crystal field to a characteristic radius of the vacancy-vacancy interaction. There are signatures of the orientational order and of spatial voids in the vacancy distributions for some crystal field potentials. The crystal field stabilizes the patterns after they are formed, resulting in a non-volatile switching of the simulated devices.
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84.32.Ff Conductors, resistors (including thermistors, varistors, and photoresistors)

On the role of acoustic waves (phonons) in equilibrium heat exchange across a vacuum gap

Bair V. Budaev and David B. Bogy

Appl. Phys. Lett. 99, 053109 (2011); http://dx.doi.org/10.1063/1.3623433 (3 pages) | Cited 1 time

Online Publication Date: 3 August 2011

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Heat exchange between closely positioned bodies has become an important issue for such areas of modern technology as integrated circuits, atomic force microscopy, and high-density magnetic recording, which deal with bodies separated by gaps as narrow as a few nanometers. This paper shows that if the gap’s width is below a certain value, estimated as about 10 nm for silicon at room temperature, then, in addition to electromagnetic radiation, significant heat is also carried by acoustic waves. Moreover, as the width of the gap decreases below about 5 nm, acoustic waves rapidly become the dominant heat carrier.
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62.65.+k Acoustical properties of solids
75.50.Ss Magnetic recording materials
63.22.Kn Clusters and nanocrystals

From microns to kissing contact: Dynamic positioning of two nano-systems

Kevin J. Savage, Matthew M. Hawkeye, Bruno F. Soares, and Jeremy J. Baumberg

Appl. Phys. Lett. 99, 053110 (2011); http://dx.doi.org/10.1063/1.3623437 (3 pages) | Cited 1 time

Online Publication Date: 3 August 2011

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Two conducting atomic force microscopy probes are brought into three-dimensional nanoscale “tip-to-tip” alignment with dynamically controlled spacing and ultra-wide optical access. We utilize resonant electrical parametric mixing, created by the electromechanically coupled tips, to extract the electronic signal due to nanoscale changes in inter-tip position. Experimental results match theory confirming the viability of the technique. By functionalizing the tip apexes, this advanced multi-functional observation platform allows simultaneous measurement of the optical and electronic response of nanoparticle dimers, at sub-nanometer separations.
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73.22.-f Electronic structure of nanoscale materials and related systems
78.67.Bf Nanocrystals, nanoparticles, and nanoclusters

Energy-loss rate of a fast particle in graphene

Yee Sin Ang, C. Zhang, and Chun Yun Kee

Appl. Phys. Lett. 99, 053111 (2011); http://dx.doi.org/10.1063/1.3615795 (3 pages)

Online Publication Date: 3 August 2011

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The energy-loss rate of a fast particle in graphene is studied. The energy-loss rate always increases with increasing incident particle energy, which is quite unusual when compared to electron gas in normal metal. Graphene exhibits a “discriminating” behavior where there exists a low energy cut-off below which the scattering process is strictly forbidden, leading to lossless traverse of an external particle in graphene. This low energy cutoff is of the order of nearest neighbor hopping bandwidth. Our results suggest that backscattering is also absent in the external particle scattering of graphene.
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61.85.+p Channeling phenomena (blocking, energy loss, etc.)

Tip-enhanced Raman mapping of a single Ge nanowire

Y. Ogawa, Y. Yuasa, F. Minami, and S. Oda

Appl. Phys. Lett. 99, 053112 (2011); http://dx.doi.org/10.1063/1.3621856 (3 pages) | Cited 7 times

Online Publication Date: 3 August 2011

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We report the nanometer scale mapping of a single Ge nanowire (NW) using tip-enhanced Raman scattering (TERS). The Raman spectra of a single Ge NW show downshift and asymmetric broadening, depending on the diameter, due to the phonon confinement effect. A Raman peak attributed to amorphous Ge has also been observed. Assuming the crystalline core/amorphous shell structure, we estimate the amorphous shell thickness to be 2–6 monolayers from the integrated Raman intensities of crystalline and amorphous Ge.
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78.67.Uh Nanowires
64.70.Nd Structural transitions in nanoscale materials
78.30.Am Elemental semiconductors and insulators
78.35.+c Brillouin and Rayleigh scattering; other light scattering
63.22.Gh Nanotubes and nanowires

Diffusion limited current in very high aspect ratio Pt needle electrodes

Jie Hu, Kyungsuk Yum, Arash Tajik, Majid Minary-Jolandan, Jeahoon Bang, and Min-Feng Yu

Appl. Phys. Lett. 99, 053113 (2011); http://dx.doi.org/10.1063/1.3621875 (3 pages)

Online Publication Date: 3 August 2011

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A direct-write nanofabrication technique was applied to fabricate high aspect ratio Pt needle electrodes for site specific electrochemistry and electrophysiology. Non-passivated and passivated (with a 10 nm thin insulating film) Pt needles having uniform radii as small as 100 nm and lengths over 30 μm were deposited on the exposed conductive ends of ultramicroelectrodes to form extended needle electrodes. Diffusion limited current and its dependence on the radius of the Pt needle were measured with linear sweep voltammetry. Model fittings validated the function of such needle electrodes for effective microscale electrochemical studies and potentially electrophysiological applications.
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66.30.Fq Self-diffusion in metals, semimetals, and alloys
81.15.Pq Electrodeposition, electroplating
82.45.Bb Corrosion and passivation
82.45.Fk Electrodes
82.45.Qr Electrodeposition and electrodissolution
82.80.Fk Electrochemical methods

Tailoring oxidation degrees of graphene oxide by simple chemical reactions

Gongkai Wang, Xiang Sun, Changsheng Liu, and Jie Lian

Appl. Phys. Lett. 99, 053114 (2011); http://dx.doi.org/10.1063/1.3622637 (3 pages) | Cited 6 times

Online Publication Date: 4 August 2011

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High quality graphene oxide (GO) with controllable degrees of oxidation was synthesized by simple chemical reactions inspired by approaches to unzip single wall carbon nanotubes using strong oxidizing agents. As compared to the conventional Hummers method, these reactions are less exo-therm involved without emission of toxic gases. The structural characteristics of the synthesized GO with various oxidation degrees were evaluated by x-ray diffraction, x-ray photoelectron spectroscopy, Raman spectroscopy, thermal gravimetric analysis, and UV-vis-IR spectroscopy. GO with tailored degrees of oxidation displays tunable optoelectronic properties and may have a significant impact on developing graphene- or GO-based platforms for various technological applications.
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81.05.ue Graphene
78.30.Na Fullerenes and related materials
78.40.Ri Fullerenes and related materials
79.60.Bm Clean metal, semiconductor, and insulator surfaces
82.80.Pv Electron spectroscopy (X-ray photoelectron (XPS), Auger electron spectroscopy (AES), etc.)
61.48.Gh Structure of graphene

Self-assembled Si/SiO2 superlattice in Si-rich oxide films

Chu-Yun Hsiao (蕭竹芸), Chuan-Feng Shih (施權峰), Kuan-Wei Su (蘇冠瑋), Hui-Ju Chen (陳惠茹), and Sheng-Wen Fu (傅聖文)

Appl. Phys. Lett. 99, 053115 (2011); http://dx.doi.org/10.1063/1.3624706 (3 pages) | Cited 1 time

Online Publication Date: 4 August 2011

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This work involves as-prepared SiOx (x ≤ 2) films that were deposited by reactive sputtering. The regular Si/SiO2 superlattices were self-assembled without post-annealing. The periodicity of Si/SiO2 superlattices was modulated by varying the oxygen flow rate and was associated with x in SiOx in the range 2–1.3. Si/SiO2 superlattices were formed under compressive stress and the factors that governed the periodicity were discussed.
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81.15.Cd Deposition by sputtering
68.55.A- Nucleation and growth
81.05.Cy Elemental semiconductors

Modification of spontaneous emission rates in single colloidal CdSe/ZnS quantum dots by a submicron-sized dielectric disk

C. T. Yuan, Y. C. Wang, Y. C. Yang, M. C. Wu, Jau Tang, and M. H. Shih

Appl. Phys. Lett. 99, 053116 (2011); http://dx.doi.org/10.1063/1.3622641 (3 pages) | Cited 2 times

Online Publication Date: 4 August 2011

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The spontaneous emission (SE) of light sources can be modified externally by surrounding local density of optical states. Here, the SE of single colloidal CdSe/ZnS quantum dots (QDs) coupled to dielectric disks with sub-micrometer sizes was investigated. Using single-QD measurement, the radiative decay rates can be extracted based on time-tagged, time-resolved measurement. In this case, up to ∼6-fold enhancement of the SE rate was observed when single QDs were located on the disk edge. In addition, the photon statistic was found to exhibit photon anti-bunching behavior with much narrowing linewidth, indicating single-photon emission via fast radiative decay process.
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78.67.Hc Quantum dots
78.47.jd Time resolved luminescence
78.55.Et II-VI semiconductors

Origin of the high p-doping in F intercalated graphene on SiC

Y. C. Cheng, T. P. Kaloni, G. S. Huang, and U. Schwingenschlögl

Appl. Phys. Lett. 99, 053117 (2011); http://dx.doi.org/10.1063/1.3623484 (3 pages) | Cited 13 times

Online Publication Date: 4 August 2011

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The atomic and electronic structures of F intercalated epitaxial graphene on a SiC(0001) substrate are studied by first-principles calculations. A three-step fluorination process is proposed. First, F atoms are intercalated between the graphene and the SiC, which restores the Dirac point in the band structure. Second, saturation of the topmost Si dangling bonds introduces p-doping up to 0.37 eV. Third, F atoms bond covalently to the graphene to enhance the p-doping. Our model explains the highly p-doped state of graphene on SiC after fluorination [A. L. Walter et al., Appl. Phys. Lett. 98, 184102 (2011)].
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71.20.Tx Fullerenes and related materials; intercalation compounds
73.20.At Surface states, band structure, electron density of states
61.72.up Other materials
71.15.-m Methods of electronic structure calculations

Efficient three-dimensional nanostructured photoelectric device by Al-ZnO coating on lithography-free patterned Si nanopillars

Sang-Won Jee, Seong-Je Park, Joondong Kim, Yun Chang Park, Jun-Hyuk Choi, Jun-Ho Jeong, and Jung-Ho Lee

Appl. Phys. Lett. 99, 053118 (2011); http://dx.doi.org/10.1063/1.3621877 (3 pages) | Cited 1 time

Online Publication Date: 4 August 2011

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An efficient three-dimensional (3D) nanostructure photoelectric device is presented. An Al-doped ZnO (AZO) coating was applied to lithography-free patterned Si nanopillars and spontaneously formed a radial heterojunction (n-AZO/p-Si) photodiode having a quality ideality factor of 1.64. A significantly enhanced photocurrent of 5.45 mA/cm2 was obtained from the 3D nanostructure relative to that of a planar substrate (1.1 mA/cm2). This enhancement is induced by enlargement of the light-active surface area and an anti-reflection effect. Due to the intermediate refractive index of AZO, the reflection was distinctively reduced in the air-Si system. It discusses an effective approach for realizing nanostructured photoelectric device.
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85.60.Dw Photodiodes; phototransistors; photoresistors
42.79.Wc Optical coatings
81.07.Bc Nanocrystalline materials
81.16.Rf Micro- and nanoscale pattern formation

Waveguide Fabry-Pérot microcavity arrays

Shengfei Feng, Xinping Zhang, and Peter J. Klar

Appl. Phys. Lett. 99, 053119 (2011); http://dx.doi.org/10.1063/1.3616148 (3 pages) | Cited 5 times

Online Publication Date: 4 August 2011

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Spectroscopic properties of the Fabry-Pérot (FP) microcavities arranged periodically on a dielectric waveguide are investigated theoretically. A strong coupling behavior between the waveguide resonance and the FP resonance modes is demonstrated for incident light with TE polarization. The narrow-band waveguide resonance modes are observed as asymmetric transmission peaks within the FP stop band, whereas they become transmission dips (antiresonance) in the FP pass band. The coupled mode transits between these two states as the waveguide resonance mode is tuned between the FP pass and stop bands. This transition can be explained in the Fano-picture and is important for the design of photonic devices with narrow-band and tunable optical response
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42.79.Gn Optical waveguides and couplers
42.82.-m Integrated optics

Electrical power dissipation in semiconducting carbon nanotubes on single crystal quartz and amorphous SiO2

Cheng-Lin Tsai, Albert Liao, Eric Pop, and Moonsub Shim

Appl. Phys. Lett. 99, 053120 (2011); http://dx.doi.org/10.1063/1.3622769 (3 pages) | Cited 10 times

Online Publication Date: 5 August 2011

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Heat dissipation in electrically biased individual semiconducting carbon nanotubes (CNTs) on single crystal quartz and amorphous SiO2 is examined with temperature profiles obtained by spatially resolved Raman spectroscopy. Despite the differences in phonon velocities, thermal conductivity, and van der Waals interactions with CNTs, on average, heat dissipation into single crystal quartz and amorphous SiO2 is found to be similar. Large temperature gradients and local hot spots often observed underscore the complexity of CNT temperature profiles and may be accountable for the similarities observed.
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61.46.Fg Nanotubes
78.35.+c Brillouin and Rayleigh scattering; other light scattering
81.05.Gc Amorphous semiconductors
81.07.De Nanotubes
66.70.-f Nonelectronic thermal conduction and heat-pulse propagation in solids; thermal waves
61.43.Dq Amorphous semiconductors, metals, and alloys

Transition-metal-molecular sandwich nanowires as magnetic on/off switch

Menghao Wu and Xiao Cheng Zeng

Appl. Phys. Lett. 99, 053121 (2011); http://dx.doi.org/10.1063/1.3624458 (3 pages) | Cited 4 times

Online Publication Date: 5 August 2011

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Using first-principles calculation, we predict that upon electron injection, transition-metal-benzene [Cr(Bz)]∞ and transition-metal-ferrocene [Mn(Cp)]∞ sandwich nanowires (SWNs) can switch from nonmagnetic semiconductor to magnetic half metal. The mechanism underlying this charge-induced transition is clarified through Stoner criterion. A relationship between induced magnetic moment and injected charge density is investigated. We also find that the magnetic coupling within the [Ti(Bz)]∞ SWN can be also tuned though charge injection. Upon either hole or electron injection, the ground state of [Ti(Bz)]∞ SWN can be switched from antiferromagnetic to ferromagnetic.
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73.22.Lp Collective excitations
75.30.Cr Saturation moments and magnetic susceptibilities
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
75.60.-d Domain effects, magnetization curves, and hysteresis
71.10.Hf Non-Fermi-liquid ground states, electron phase diagrams and phase transitions in model systems
71.15.-m Methods of electronic structure calculations

On the importance of optical phonons to thermal conductivity in nanostructures

Zhiting Tian, Keivan Esfarjani, Junichiro Shiomi, Asegun S. Henry, and Gang Chen

Appl. Phys. Lett. 99, 053122 (2011); http://dx.doi.org/10.1063/1.3615709 (3 pages) | Cited 7 times

Online Publication Date: 5 August 2011

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The contribution of optical phonons to thermal conductivity has typically been ignored. However, when the system size decreases to the nanoscale regime, optical phonons are no longer negligible. In this study, the contributions of different phonon polarizations to the thermal conductivity of silicon are discussed based on the phonon lifetimes extracted from a first principles approach. The results indicate that around room temperature, optical phonons can contribute over 20% to the thermal conductivity of nanostructures as compared to 5% in bulk materials. In addition, the temperature and size dependence of the contributions from acoustic and optical phonons are fully explored.
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63.22.Gh Nanotubes and nanowires
66.70.Df Metals, alloys, and semiconductors
71.15.-m Methods of electronic structure calculations
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
78.66.Db Elemental semiconductors and insulators
63.20.dk First-principles theory

Electronic structures of Fe-terminated armchair boron nitride nanoribbons

Yanli Wang, Yi Ding, and Jun Ni

Appl. Phys. Lett. 99, 053123 (2011); http://dx.doi.org/10.1063/1.3624475 (3 pages) | Cited 7 times

Online Publication Date: 5 August 2011

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Using first-principles calculations, we investigate the structural, electronic, and magnetic properties of Fe-terminated armchair boron nitride nanoribbons (Fe-ABNNRs). We find that Fe atoms can form a dimerized zigzag chain along the armchair edge. Different from the semiconducting H-terminated ABNNRs, the Fe-ABNNRs are antiferromagnetic metals. When one edge is terminated by Fe atoms and the other edge by H atoms, the ABNNRs become half-metals regardless of the ribbon width. Other transition-metal terminated nanoribbons are also examined, which are semiconductors or half-metals with diverse magnetic states depending on the types of metals.
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73.22.-f Electronic structure of nanoscale materials and related systems
75.50.Ee Antiferromagnetics
81.05.Ea III-V semiconductors
75.75.-c Magnetic properties of nanostructures
61.46.-w Structure of nanoscale materials
71.20.Nr Semiconductor compounds

Influence of the local environment on Zn acceptors in the GaAs(110) surface

D. H. Lee, N. M. Santagata, and J. A. Gupta

Appl. Phys. Lett. 99, 053124 (2011); http://dx.doi.org/10.1063/1.3624535 (3 pages) | Cited 1 time

Online Publication Date: 5 August 2011

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Individual Zn acceptors in the GaAs (110) surface layer are studied with a scanning tunneling microscope. Tunneling spectroscopy reveals a peak associated with a Zn acceptor state, whose linewidth and response to local band bending depend on proximity to neighboring subsurface Zn acceptors. Though identical in topographic images, surface-layer Zn with nearby subsurface neighbors exhibits a broad peak that is insensitive to band bending, while more isolated surface-layer Zn exhibit a narrow peak which is sensitive to band bending. These results are suggestive of a shallow-to-deep acceptor transition, driven by the random dopant distribution.
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71.55.Eq III-V semiconductors
61.72.uj III-V and II-VI semiconductors

Controlling the function of carbon nanotube devices with re-writable charge patterns

Landon Prisbrey, Tristan DeBorde, Ji-Yong Park, and Ethan D. Minot

Appl. Phys. Lett. 99, 053125 (2011); http://dx.doi.org/10.1063/1.3622138 (3 pages) | Cited 2 times

Online Publication Date: 5 August 2011

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We use atomic force microscopy lithography to write charge patterns in close proximity to carbon nanotube field-effect transistor devices. The silicon dioxide substrate retains the charge for days, allowing various charge configurations to be tested. We show that the written charge can move the Fermi level in the nanotube by 1 eV and we use this charge lithography to reconfigure a field-effect transistor into a pn junction. The substrate charge can be erased and rewritten, offering a new tool for prototyping nanodevices and optimizing electrostatic doping profiles.
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85.30.Tv Field effect devices
85.35.Kt Nanotube devices
85.40.Hp Lithography, masks and pattern transfer
85.40.Ry Impurity doping, diffusion and ion implantation technology
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