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10 Jan 2005

Volume 86, Issue 2, Articles (02xxxx)

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Appl. Phys. Lett. 86, 021101 (2005); http://dx.doi.org/10.1063/1.1849439 (3 pages)

H. W. Choi, C. W. Jeon, C. Liu, I. M. Watson, M. D. Dawson, P. R. Edwards, R. W. Martin, S. Tripathy, and S. J. Chua
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Electrical characteristics of Pt Schottky contacts on sulfide-treated n-type ZnO

Sang-Ho Kim, Han-Ki Kim, and Tae-Yeon Seong

Appl. Phys. Lett. 86, 022101 (2005); http://dx.doi.org/10.1063/1.1839285 (3 pages) | Cited 34 times

Online Publication Date: 30 December 2004

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We have investigated the effect of sulfide treatment on the electrical characteristics of Pt contacts on (000-1) n-type ZnO ( ∼ 5×1015cm−3) single crystals. The Pt contact on conventionally cleaned ZnO surface shows an ohmic behavior. However, the contact produces a Schottky behavior, when the ZnO surface is etched in a boiling (NH4)2Sx solution. Measurements show that the Schottky barrier height, ideality factor, and leakage current at −5 V of the Pt contact on the sulfide-treated ZnO are 0.79 eV, 1.51, and 3.75×10−10 A, respectively. Auger electron spectroscopy (AES) and x-ray photoelectron spectroscopy (XPS) examinations indicate the formation of ZnS phase at the Pt/ZnO interface. Based on the capacitance–voltage, AES, and XPS results, a possible mechanism for the formation of good Schottky contacts is given.
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81.05.Bx Metals, semimetals, and alloys
81.05.Dz II-VI semiconductors
73.40.Ns Metal-nonmetal contacts
73.30.+y Surface double layers, Schottky barriers, and work functions
81.65.Cf Surface cleaning, etching, patterning
79.60.Bm Clean metal, semiconductor, and insulator surfaces
79.60.Jv Interfaces; heterostructures; nanostructures
68.37.Xy Scanning Auger microscopy, photoelectron microscopy

Ballistic transport mode detected by picosecond time-of-flight measurements for nanocrystalline porous silicon layer

Akira Kojima and Nobuyoshi Koshida

Appl. Phys. Lett. 86, 022102 (2005); http://dx.doi.org/10.1063/1.1848181 (3 pages) | Cited 9 times

Online Publication Date: 30 December 2004

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The electron transport mechanism in nanocrystalline porous silicon (nc-PS) with a controlled structure has been studied for a self-supporting sample by time-of-flight (TOF) measurements at room and low temperatures using a picosecond-width UV laser pulse. In contrast to both single-crystalline silicon (c‐Si) and hydrogenated amorphous silicon (a‐Si:H), the TOF signals of nc-PS show characteristic behavior that involves a ballistic component. The drift velocity vd determined from observed TOF signals shows no signs of saturation with increasing field strength F. At F ∼ 3×104 V/cm, the vd value in nc-PS at room temperature reaches 2.2×108 cm/s. The corresponding electron mean free path is 1.6 μm. These values are considerably larger than those in c‐Si. The ballistic transport mode becomes clear at low temperatures. The results support the model that electrons can travel ballistically with little scattering losses in a nanocrystalline silicon dot chain interconnected via thin silicon dioxide films.
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73.63.Bd Nanocrystalline materials
73.23.Ad Ballistic transport
79.60.Bm Clean metal, semiconductor, and insulator surfaces
79.60.Jv Interfaces; heterostructures; nanostructures

Single-crystal field-effect transistors based on copper phthalocyanine

R. Zeis, T. Siegrist, and Ch. Kloc

Appl. Phys. Lett. 86, 022103 (2005); http://dx.doi.org/10.1063/1.1849438 (3 pages) | Cited 79 times

Online Publication Date: 3 January 2005

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Copper phthalocyanine (Cu–Pc) single crystals were grown by physical vapor transport and field-effect transistors (FETs) on the surface of these crystals were prepared. These FETs function as p-channel accumulation-mode devices. Charge carrier mobilities of up to 1 cm2/V s combined with a low field-effect threshold were obtained. These remarkable FET characteristics, along with the highly stable chemical nature of Cu–Pc, make it an attractive candidate for device applications.
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85.30.Tv Field effect devices
72.20.Fr Low-field transport and mobility; piezoresistance
72.80.Le Polymers; organic compounds (including organic semiconductors)
81.10.Bk Growth from vapor

Direct comparison of field-effect and electrochemical doping in regioregular poly(3-hexylthiophene)

Hidekazu Shimotani, Gildas Diguet, and Yoshihiro Iwasa

Appl. Phys. Lett. 86, 022104 (2005); http://dx.doi.org/10.1063/1.1850614 (3 pages) | Cited 55 times

Online Publication Date: 3 January 2005

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We have measured carrier mobility of regioregular poly(3-hexylthiophene) films by both field-effect and electrochemical doping on identical devices, which allowed us a direct comparison between the two doping processes. The carrier mobility of electrochemical doping at low doping levels was lower than that of field-effect doping by two orders of magnitudes, while that of electrochemical doping steeply increased with doping levels, reaching comparable or higher values than that of field-effect doping. These results are attributable to carrier trapping by the Coulomb potentials of dopant anions at low doping levels, demonstrating a significant difference between field-effect and chemical doping.
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85.30.Tv Field effect devices
61.72.up Other materials
73.61.Ph Polymers; organic compounds
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths
73.50.Dn Low-field transport and mobility; piezoresistance
61.72.S- Impurities in crystals
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.

Evaluation of nickel and molybdenum silicides for dual gate complementary metal-oxide semiconductor application

Nivedita Biswas, Jason Gurganus, Veena Misra, Yan Yang, and Susanne Stemmer

Appl. Phys. Lett. 86, 022105 (2005); http://dx.doi.org/10.1063/1.1849850 (3 pages) | Cited 6 times

Online Publication Date: 4 January 2005

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Characteristics of NiSi and MoSi via full consumption of undoped silicon layers have been studied. Interaction of nickel (Ni) and molybdenum (Mo) silicides with SiO2 was evaluated in terms of work function and thermal stability. For nickel silicide, the work function values were low for samples annealed at 400 °C even after full consumption of silicon. The work function increased with the anneal temperature and stabilized at 600 °C to close to midgap values. Dielectric interaction as a result of silicide formation was studied using current–voltage characteristics. Low leakage currents in these stacks indicated minimum dielectric damage due to silicided gates. Silicidation of Mo was found to be incomplete as the capacitance–voltage curves were marked with larger EOT values and negative shifts in the flatband voltages even at 700 °C. Auger depth profiling, high resolution transmission electron microscopy (HRTEM) and x-ray diffraction (XRD) were used for material analysis of the silicided gate stacks.
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73.61.Ng Insulators
73.30.+y Surface double layers, Schottky barriers, and work functions
61.72.Cc Kinetics of defect formation and annealing
77.84.Bw Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.
68.55.-a Thin film structure and morphology
68.55.Nq Composition and phase identification
68.37.Lp Transmission electron microscopy (TEM)

Ultrahigh temperature vibration sensors using aluminum nitride thin films and W/Ru multilayer electrodes

Morito Akiyama, Toshihiro Kamohara, Keiko Nishikubo, Naohiro Ueno, Hideaki Nagai, and Takeshi Okutani

Appl. Phys. Lett. 86, 022106 (2005); http://dx.doi.org/10.1063/1.1850193 (3 pages) | Cited 1 time

Online Publication Date: 4 January 2005

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Ultrahigh temperature vibration sensors have been fabricated from highly c-axis-oriented aluminum nitride (AlN) thin films and tungsten/ruthenium (W/Ru) multilayer bottom electrodes. These films and electrodes were prepared by radio-frequency magnetron sputtering on zirconium oxide (ZrO2) substrates, such as AlN/W/Ru/ZrO2. The vibration sensors resisted the heat treatment of 1450 °C for 1 h in argon, and after that, peeling and cracks were not observed in the sensor surface. The “tough” behavior of the vibration sensors in the high temperature is probably attributed to the chemical composition change of the W/Ru multilayer bottom electrodes to Ru60W40 and Ru15W85 solid solutions that prevent chemical reactions and relax thermal stress.
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07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing
85.50.-n Dielectric, ferroelectric, and piezoelectric devices
07.10.Pz Instruments for strain, force, and torque
68.60.Bs Mechanical and acoustical properties
81.40.Np Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure
77.55.-g Dielectric thin films
82.33.-z Reactions in various media
68.35.Gy Mechanical properties; surface strains
62.20.M- Structural failure of materials
77.65.-j Piezoelectricity and electromechanical effects
81.40.Gh Other heat and thermomechanical treatments

Hot-electron transport in 4H–SiC

L. Ardaravičius, A. Matulionis, O. Kiprijanovic, J. Liberis, H.-Y. Cha, L. F. Eastman, and M. G. Spencer

Appl. Phys. Lett. 86, 022107 (2005); http://dx.doi.org/10.1063/1.1851001 (3 pages) | Cited 4 times

Online Publication Date: 5 January 2005

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Nanosecond-pulsed technique is used to study hot-electron transport in donor-doped 4H–SiC (n = 2×1017 cm−3) biased parallel to the basal plane. The measurements of current with 1 ns voltage pulses are carried out at average electric fields up to 570 kV/cm. A region with a negative differential conductance is observed for the range of fields exceeding 280 kV/cm, followed by a sharp increase in the current at fields over 345 kV/cm. The dependence of drift velocity on electric field is deduced for the field range below the onset of the negative differential conductance to appear: the value of the saturation velocity is estimated as 1.4×107 cm/s at room temperature.
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72.20.Ht High-field and nonlinear effects
72.20.Fr Low-field transport and mobility; piezoresistance
72.80.Jc Other crystalline inorganic semiconductors

Distribution of electrically active defects in chemical vapor deposition diamond: Model and measurement

A. Balducci, Marco Marinelli, E. Milani, M. E. Morgada, G. Pucella, G. Rodriguez, A. Tucciarone, G. Verona-Rinati, M. Angelone, and M. Pillon

Appl. Phys. Lett. 86, 022108 (2005); http://dx.doi.org/10.1063/1.1842856 (3 pages) | Cited 7 times

Online Publication Date: 5 January 2005

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Defects limiting the movement of charge carriers in polycrystalline chemical vapor deposition (CVD) diamond films are located within the grains or in grain boundaries. Their geometrical distribution in the sample is different and is usually unknown. We present here a method to quantitatively evaluate the concentration and distribution of in-grain and grain-boundary located active carrier traps. Since the impact of these two kinds of defects on the performance of CVD diamond based devices is different, it is possible to obtain the defect distribution by measuring the response of diamond alpha particle detectors as a function of film thickness. The Hecht theory, describing the efficiency of a semiconductor particle detector, has been modified to take into account the polycrystalline nature of CVD diamond. This extended Hecht model was then used to fit experimental data and extract quantitative information about the defect distribution.
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68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
61.72.Mm Grain and twin boundaries
73.61.Cw Elemental semiconductors
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths
73.50.Dn Low-field transport and mobility; piezoresistance
68.55.-a Thin film structure and morphology

Electronic insulator-conductor conversion in hydride ion-doped 12CaO∙7Al2O3 by electron-beam irradiation

Katsuro Hayashi, Yoshitake Toda, Toshio Kamiya, Masahiro Hirano, Minako Yamanaka, Isao Tanaka, Takahisa Yamamoto, and Hideo Hosono

Appl. Phys. Lett. 86, 022109 (2005); http://dx.doi.org/10.1063/1.1852723 (3 pages) | Cited 9 times

Online Publication Date: 6 January 2005

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We report formation of persistent carrier electrons in hydride ion (H−)-incorporated 12CaO∙7Al2O3 (C12A7) by electron-beam irradiation. The electrical conductivity of H−-doped C12A7 single crystals increases with the electron-beam irradiation dose, accompanied with a green coloration attributable to a carrier electron formation. A 25 keV electron beam with a dose of ∼ 500 μC cm−2 fully converts the conductivity in surface layers to the depth of ∼ 4 μm. Carrier electron formation is most likely due to electron-hole pairs generated in the electron excitation volume and subsequent energy transfer to the H− ions. The estimated carrier formation yield per an incident electron is ∼ 30. These findings may enable a fine patterning of the conductive area without photomasks and photoresists.
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73.50.-h Electronic transport phenomena in thin films
74.25.-q Properties of superconductors
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