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24 Jan 2000

Volume 76, Issue 4, pp. 397-519

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Coulomb-blockade effect observed at room temperature in Ge nanocrystalline films deposited by the cluster-beam evaporation technique

Souri Banerjee, S. Nozaki, and H. Morisaki

Appl. Phys. Lett. 76, 445 (2000); http://dx.doi.org/10.1063/1.125782 (3 pages) | Cited 6 times

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The temperature-dependent current–voltage (I–V) characteristics have been studied across the thickness of Ge nanocrystalline films prepared by the cluster beam evaporation technique. It is found that a film with a thickness of 30 nm, deposited on a substrate kept at 77 K, does not exhibit any distinct step-like feature in the I–V characteristics at room temperature. However, with the lowering of the temperature, a “Coulomb gap” is observed and a pronounced step-like feature appear in the I–V characteristics suggesting the Coulomb blockade (CB) effect. It is hypothesized that the observed CB effect in these nanocrystalline thin films results from a very highly selective electron transport process where the electron transport is dominated by one local well-defined current path with the largest conductance. The result of similar measurements on a photo-oxidized sample, which shows a signature of a step-like feature in the I–V characteristics, even at room temperature, supports this hypothesis. © 2000 American Institute of Physics.
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73.61.Cw Elemental semiconductors
73.63.-b Electronic transport in nanoscale materials and structures
73.23.Hk Coulomb blockade; single-electron tunneling
81.07.-b Nanoscale materials and structures: fabrication and characterization
81.15.Jj Ion and electron beam-assisted deposition; ion plating
81.05.Cy Elemental semiconductors

Anisotropic conduction behavior in metal-induced laterally crystallized polycrystalline silicon thin films

Mingxiang Wang, Zhiguo Meng, and Man Wong

Appl. Phys. Lett. 76, 448 (2000); http://dx.doi.org/10.1063/1.125783 (3 pages) | Cited 9 times

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The conduction behavior of metal-induced laterally crystallized (MILC) polycrystalline silicon (poly-Si) was studied and compared to that of the conventional solid-phase crystallized and low-pressure chemical vapor deposited poly-Si. MILC poly-Si was found to exhibit superior electrical properties, with significantly lower grain-boundary (GB) trap density, as well as much higher carrier mobility and conductivity. Furthermore, a unique anisotropic conduction behavior was discovered in MILC poly-Si, with the resistivity and its activation energy showing remarkable difference for conduction transverse or parallel to the MILC direction. These phenomena have been related to the fluctuation of the potential barrier associated with the longitudinal GBs separating the relatively ordered elongated grains in MILC poly-Si. © 2000 American Institute of Physics.
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73.61.Cw Elemental semiconductors
73.50.Dn Low-field transport and mobility; piezoresistance
61.72.Mm Grain and twin boundaries

Integration and electrical properties of diffusion barrier for high density ferroelectric memory

Yoon J. Song, H. H. Kim, Sung Y. Lee, D. J. Jung, B. J. Koo, J. K. Lee, Y. S. Park, H. J. Cho, S. O. Park, and Kinam Kim

Appl. Phys. Lett. 76, 451 (2000); http://dx.doi.org/10.1063/1.125784 (3 pages) | Cited 24 times

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A reliable Ir diffusion barrier was prepared on polysilicon plugged substrate with a contact size of 0.6 μm. Using a Ti adhesion layer and stress-relief process, it was possible to integrate the Ir barrier into a high density 4 Mb ferroelectric random access memory device. After heat treating sol-gel derived Pb(Zr1−xTix)O3 (PZT) films at 700 °C, the Ir barrier contact displayed an ohmic behavior and showed a low resistance of 130 Ω per contact in 1k serial contact array. The PZT films on Pt/IrO2/Ir poly-plugged substrate exhibited excellent ferroelectric properties such as remnant polarization and coercive voltage of 25 μC/cm2 and 1.15 V, respectively. Auger depth profile and transmission electron microscopy analyses confirmed that no appreciable oxidation was formed between the Ir barrier and the polysilicon plug. © 2000 American Institute of Physics.
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85.50.-n Dielectric, ferroelectric, and piezoelectric devices
84.30.Sk Pulse and digital circuits
77.22.Ej Polarization and depolarization
68.35.Fx Diffusion; interface formation

A pump and probe study of photoinduced internal field screening dynamics in an AlGaN/GaN single-quantum-well structure

A. Shikanai, T. Deguchi, T. Sota, T. Kuroda, A. Tackeuchi, S. Chichibu, and S. Nakamura

Appl. Phys. Lett. 76, 454 (2000); http://dx.doi.org/10.1063/1.125785 (3 pages) | Cited 10 times

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Photogenerated carrier dynamics in an AlGaN/GaN single quantum well has been studied using a conventional degenerate pump and probe technique at room temperature. Photoinduced absorption at the exciton resonance has been observed. It is explained by the absorption coefficient change, through the quantum-confined Stark effect and the quantum-confined Franz–Keldish effect, caused by the photoinduced internal electric-field screening. In comparison with biased GaAs multiple quantum wells, a slower time evolution of differential transmission signals has been also found. Its origin is attributed to the longer carrier sweep-out time due to the potential profile of the sample in conjunction with the longer carrier recombination time. © 2000 American Institute of Physics.
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78.66.Fd III-V semiconductors
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
71.35.-y Excitons and related phenomena
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
78.20.Jq Electro-optical effects
78.47.-p Spectroscopy of solid state dynamics
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths
73.61.Ey III-V semiconductors

Fabrication of a single-electron transistor by current-controlled local oxidation of a two-dimensional electron system

U. F. Keyser, H. W. Schumacher, U. Zeitler, R. J. Haug, and K. Eberl

Appl. Phys. Lett. 76, 457 (2000); http://dx.doi.org/10.1063/1.125786 (3 pages) | Cited 42 times

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The surface layers of a GaAs/AlGaAs heterostructure are locally oxidized using an atomic force microscope. The local anodic oxidation depletes the underlying two-dimensional electron gas leading to the formation of tunneling barriers. The height of the barriers is determined by measuring the thermally activated current. By varying the oxidation current, the barrier heights can be tuned between a few meV and more than 100 meV. Using these barriers as tunneling elements, a side gated single-electron transistor is fabricated. © 2000 American Institute of Physics.
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85.35.Gv Single electron devices
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
81.65.Mq Oxidation
73.23.Hk Coulomb blockade; single-electron tunneling
07.79.Lh Atomic force microscopes

Electronic bistability in electrochemically self-assembled quantum dots: A potential nonvolatile random access memory

N. Kouklin, S. Bandyopadhyay, S. Tereshin, A. Varfolomeev, and D. Zaretsky

Appl. Phys. Lett. 76, 460 (2000); http://dx.doi.org/10.1063/1.125787 (3 pages) | Cited 24 times

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An electronic bistability has been observed in a two-dimensional spatially ordered array of 10 nm quantum dots self-assembled by electrodepositing CdS in nanoporous anodic alumite film. The current–voltage characteristic of the array shows switching between two stable conductance states, which can be controlled by an external bias. The bistability is observed when current flows laterally between two contacts on the top surface of the array, and also when current flows vertically between a top contact and the bottom (conducting) substrate. If the system is left in one conductance state, it remains there for at least 180 h and possibly much longer, until switched to the other state by an external bias. Such an effect may find applications in inexpensive, ultradense nonvolatile static random access memory. © 2000 American Institute of Physics.
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73.61.Ga II-VI semiconductors
72.60.+g Mixed conductivity and conductivity transitions
81.15.Pq Electrodeposition, electroplating
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
84.30.Sk Pulse and digital circuits
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems

Atomically resolved scanning tunneling microscopy of hydrogen-terminated Si(001) surfaces after HF cleaning

Kenta Arima, Katsuyoshi Endo, Toshihiko Kataoka, Yasushi Oshikane, Haruyuki Inoue, and Yuzo Mori

Appl. Phys. Lett. 76, 463 (2000); http://dx.doi.org/10.1063/1.125788 (3 pages) | Cited 25 times

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Atomic structures of hydrogen-terminated Si(001) surfaces after HF cleaning are investigated by scanning tunneling microscopy. It is revealed that the surface is macroscopically rough but is composed of terraces and steps. Inside a terrace, 1×1 structures are formed. This corresponds to the ideal 1×1 dihydride structure. The step edges run along the 〈110〉 direction. On the other hand, the 1×1 dihydride structure disappears when the surface is subsequently rinsed with ultrapure water, because every other dihydride row of the ideal 1×1 structure is preferentially etched in ultrapure water. © 2000 American Institute of Physics.
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68.35.B- Structure of clean surfaces (and surface reconstruction)
81.65.Cf Surface cleaning, etching, patterning
81.05.Cy Elemental semiconductors

Direct experimental observation of the local electronic structure at threading dislocations in metalorganic vapor phase epitaxy grown wurtzite GaN thin films

Y. Xin, E. M. James, I. Arslan, S. Sivananthan, N. D. Browning, S. J. Pennycook, F. Omnès, B. Beaumont, J-P. Faurie, and P. Gibart

Appl. Phys. Lett. 76, 466 (2000); http://dx.doi.org/10.1063/1.125789 (3 pages) | Cited 40 times

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The electronic structure of pure edge threading dislocations in metalorganic vapor phase epitaxy grown wurtzite GaN thin films has been studied directly by atomic resolution Z-contrast imaging and electron energy loss spectroscopy in a scanning transmission electron microscope. Dislocation cores in n-type samples grown in N-rich conditions show no evidence for the high concentration of Ga vacancies predicted by previous theoretical calculations. Nitrogen K-edge spectra collected from edge dislocation cores show a sudden and significant increase in the intensity of the first fine-structure peak immediately above the edge onset compared to the bulk spectra. The origin of this increase is discussed. © 2000 American Institute of Physics.
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71.55.Eq III-V semiconductors
61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)
79.20.Kz Other electron-impact emission phenomena
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
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