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19 Mar 1990

Volume 56, Issue 12, pp. 1083-1188

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Molecular field‐effect transistors using conducting polymer Langmuir–Blodgett films

J. Paloheimo, P. Kuivalainen, H. Stubb, E. Vuorimaa, and P. Yli‐Lahti

Appl. Phys. Lett. 56, 1157 (1990); http://dx.doi.org/10.1063/1.103182 (3 pages) | Cited 116 times

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Thin‐film field‐effect transistors (FETs) have been prepared using poly(3‐hexylthiophene)/ arachidic acid and quinquethiophene/arachidic acid Langmuir–Blodgett (LB) films with thicknesses ranging from a monolayer to some ten monolayers. The effect of the number of layers on the mobility and conductivity has been studied. This is to our knowledge the first demonstration of a LB FET utilizing organic semiconductors as the active material.
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73.61.Cw Elemental semiconductors
73.61.Jc Amorphous semiconductors; glasses
73.61.Le Other inorganic semiconductors
73.50.Dn Low-field transport and mobility; piezoresistance
72.20.Fr Low-field transport and mobility; piezoresistance
85.30.Tv Field effect devices

Observation of a correlation between twin orientation and substrate step direction in thin GaAs films grown on intentionally misoriented Si (100)

K. C. Rajkumar, A. Madhukar, J. K. Liu, and F. J. Grunthaner

Appl. Phys. Lett. 56, 1160 (1990); http://dx.doi.org/10.1063/1.102549 (3 pages) | Cited 6 times

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A transmission electron microscope study of GaAs grown on Si tilted 4° off (100) has for the first time revealed that of the two twin variants propagating to the GaAs film surface, a substrate tilt about a 〈011〉‐type direction favors one over the other.
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81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
61.72.Nn Stacking faults and other planar or extended defects

Molecular beam epitaxy of Zn1−xCdxSe epilayers and ZnSe/Zn1−xCdxSe superlattices

N. Samarth, H. Luo, J. K. Furdyna, R. G. Alonso, Y. R. Lee, A. K. Ramdas, S. B. Qadri, and N. Otsuka

Appl. Phys. Lett. 56, 1163 (1990); http://dx.doi.org/10.1063/1.102550 (3 pages) | Cited 87 times

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We have investigated the epitaxial growth of Zn1−x CdxSe epilayers and ZnSe/Zn1−x CdxSe superlattices (0≤x≤1) on (100)GaAs. Although thick epilayers of Zn1−x CdxSe are prone to defect formation with increasing Cd content, the structural and optical characteristics improve remarkably when Zn1−x CdxSe is  in the  form of  thin layers  within ZnSe/Zn1−x CdxSe  superlattices. High  quality superlattices  can be grown for x≤0.35. The characterization of these systems using transmission electron microscopy, x‐ray diffraction, reflectivity, and photoluminescence is reported.
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81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties

Growth of CdTe by organometallic vapor phase epitaxy in an impinging jet reactor

D. W. Snyder, E. I. Ko, P. J. Sides, and S. Mahajan

Appl. Phys. Lett. 56, 1166 (1990); http://dx.doi.org/10.1063/1.102551 (3 pages) | Cited 6 times

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Deposition of (100)CdTe epilayers by organometallic vapor phase epitaxy (OMVPE) has been investigated using a vertical downward flowing impinging jet reactor with dimethylcadmium (DMCd) and diethyltelluride (DETe) as the organometallic sources. An Arrhenius plot of deposition rate versus substrate temperature had a linear region over a wide temperature range from 320 to 480 °C, corresponding to an activation energy for growth of 18 kcal/mol. Surfaces of (100)CdTe epilayers had high densities of pyramidal hillocks. Double‐crystal x‐ray rocking curves, however, were not affected by the presence of the hillocks. Full widths at half maximum for the (400) reflection of less than 30 arcsec were obtained for growth temperatures from 400 to 480 °C. At 460 °C rocking curves for the epilayer were nearly identical to the substrate demonstrating that films whose quality matches that of the underlying substrate can be deposited in the impinging jet system.
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81.15.Kk Vapor phase epitaxy; growth from vapor phase
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

Correlation of modulated optical reflectance with silicon carrier lifetime and impurity concentration

G. A. Rozgonyi, Z. J. Radzimski, R. R. Kola, W. L. Smith, and A. Bivas

Appl. Phys. Lett. 56, 1169 (1990); http://dx.doi.org/10.1063/1.102552 (3 pages)

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Modulated optical reflectance imaging using a scanning dual laser apparatus is a new, nondestructive tool for the characterization of semiconductor surfaces. One can expect that semiconductor material parameters such as doping concentration, impurity and damage level, which influence the minority‐carrier lifetime and diffusion length, may also influence the magnitude of the modulated reflectance signal. A semi‐quantitative correlation is presented for multilayer epitaxially grown structures with germanium and boron‐induced dislocations, as well as on their Czochralski silicon substrates, which contain a denuded zone.
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72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
61.72.sd Impurity concentration
61.72.sh Impurity distribution
61.72.sm Impurity gradients

Atomic layer epitaxy of GaInP ordered alloy

B. T. McDermott, K. G. Reid, N. A. El‐Masry, S. M. Bedair, W. M. Duncan, X. Yin, and Fred H. Pollak

Appl. Phys. Lett. 56, 1172 (1990); http://dx.doi.org/10.1063/1.102553 (3 pages) | Cited 38 times

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We report on the successful growth of ordered GaInP by atomic layer epitaxy on a GaAs substrate. The growth was achieved by alternate exposures to TEI, PH3, TMGa, and PH3 fluxes, and epilayers were found to closely match the GaAs substrate irrespective of the growth conditions. Room‐temperature photoreflectance results indicate a band gap of 1.78 eV, the lowest value yet reported for such ordered alloys. Photoluminescence shows an anomalous temperature dependence behavior and transmission electron microscopy studies indicate that ordering takes place preferentially on (111) alternating planes.
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81.15.-z Methods of deposition of films and coatings; film growth and epitaxy

Rapid chemical vapor deposition of superconducting YBa2Cu3Ox

W. J. Lackey, W. B. Carter, John A. Hanigofsky, D. N. Hill, E. Kent Barefield, Galina Neumeier, David F. O’Brien, Michael J. Shapiro, John R. Thompson, Andrew J. Green, Thomas S. Moss, R. A. Jake, and K. R. Efferson

Appl. Phys. Lett. 56, 1175 (1990); http://dx.doi.org/10.1063/1.103330 (3 pages) | Cited 16 times

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A process has been developed that enables the rapid chemical vapor deposition of superconducting YBa2Cu3Ox. In this process a finely ground mixture of Y(tmhd)3, Ba(tmhd)2, and Cu(tmhd)2 (tmhd=2,2,6,6‐tetramethyl‐3,5‐heptanedionate) is slowly fed, and pneumatically transported, directly into the chemical vapor deposition furnace. Because vaporizers are not used, the number of process parameters that must be controlled is greatly reduced. Deposition rates are at least an order of magnitude greater than those achieved by reagent sublimation. Films have been characterized by scanning electron microscopy, energy dispersive x‐ray spectroscopy, x‐ray diffraction, and resistance versus temperature measurements. Films produced on planar MgO substrates have Tc values that are significantly higher than previously reported for MgO.
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81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
74.78.-w Superconducting films and low-dimensional structures
74.70.-b Superconducting materials other than cuprates
74.25.Sv Critical currents
74.62.Bf Effects of material synthesis, crystal structure, and chemical composition

Microwave properties of highly oriented YBa2Cu3O7−x thin films

A. Inam, X. D. Wu, L. Nazar, M. S. Hegde, C. T. Rogers, T. Venkatesan, R. W. Simon, K. Daly, H. Padamsee, J. Kirchgessner, D. Moffat, D. Rubin, Q. S. Shu, D. Kalokitis, A. Fathy, et al.

Appl. Phys. Lett. 56, 1178 (1990); http://dx.doi.org/10.1063/1.103331 (3 pages) | Cited 71 times

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We have performed intra‐ and extra‐cavity microwave frequency (1–100 GHz) measurements on high quality Y1Ba2Cu3O7−x superconducting thin films on (100) LaAlO3 substrates. The ∼0.3 μm thin films fabricated by the pulsed laser deposition technique exhibit superconducting transition temperatures >90 K, as determined by resistivity and ac susceptibility measurements, and critical current densities of 5×106 A/cm2 at 77 K. Moreover, ion beam channeling minimum yields of ∼3% were measured, indicating the extremely high crystalline quality of films grown on the LaAlO3 substrate. Microwave surface resistance values at 77 K for these films are found to be more than one to two orders of magnitude lower than for copper at 77 K for almost the entire frequency range explored. We postulate that the reason we observe such low surface resistances in these films is the virtual absence of grain and phase boundaries coupled with the high degree of crystallinity. Furthermore, we believe that the residual resistance measured below Tc is at present dominated by losses occurring in the substrate and the cavities rather than by losses intrinsic to the Y‐Ba‐Cu oxide superconductor.
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74.25.N- Response to electromagnetic fields
74.70.-b Superconducting materials other than cuprates
68.55.-a Thin film structure and morphology
74.78.-w Superconducting films and low-dimensional structures

Theory of magnetic force microscope images

David W. Abraham and F. Alan McDonald

Appl. Phys. Lett. 56, 1181 (1990); http://dx.doi.org/10.1063/1.102554 (3 pages) | Cited 16 times

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A model is presented for magnetic force microscope (MFM) images obtained with a ferromagnetic tip and a ferromagnetic sample. Results of calculations are compared to recent MFM experiments and show good agreement using known values for magnetic parameters characterizing tip and sample. The model describes a limit in resolution determined by the demagnetizing effect of tip and sample, predicts the appearance of a novel image artifact which is particularly observable in images of narrow domains of reversed magnetization, and suggests an explanation for the observed contrast between regions of opposite magnetization.
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07.55.-w Magnetic instruments and components
68.37.-d Microscopy of surfaces, interfaces, and thin films

Infrared spectra and electron spin resonance of vanadium deep level impurities in silicon carbide

J. Schneider, H. D. Müller, K. Maier, W. Wilkening, F. Fuchs, A. Dörnen, S. Leibenzeder, and R. Stein

Appl. Phys. Lett. 56, 1184 (1990); http://dx.doi.org/10.1063/1.102555 (3 pages) | Cited 62 times

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Trace impurities of vanadium in Lely‐grown silicon carbide single crystals have been detected by their strong, polytype‐specific photoluminescence in the 1.3–1.5 μm near‐infrared spectral range, as well as by infrared absorption. The spectra arise from the intra‐3d‐shell transitions 2E(3d1)→2T2(3d1) of V4+Si(3d1). Electron spin resonance reveals that VSi in SiC acts as a deep acceptor, V4+Si(3d1)/V3+Si(3d2)−A0/A−, and possibly also as a deep donor. The role of vanadium as minority‐carrier lifetime killer in SiC‐based optoelectronic devices is suggested from these data.
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78.30.-j Infrared and Raman spectra
78.40.Fy Semiconductors
33.35.+r Electron resonance and relaxation
33.20.Ea Infrared spectra

Nonresonant absorption coefficient of single‐crystal films of polydiacetylene measured by photothermal deflection spectroscopy

M. Thakur, R. C. Frye, and B. I. Greene

Appl. Phys. Lett. 56, 1187 (1990); http://dx.doi.org/10.1063/1.102556 (2 pages) | Cited 14 times

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Using photothermal deflection spectroscopy we have measured the nonresonant absorption coefficient of poly (bis‐p‐toluene sulfonate) of 2,4 hexadiyne‐1,6 diol (PTS) single‐crystal films for the first time. The absorption coefficient continuously decreases from the reported peak value of ∼9×105 cm−1 at 620 nm (exciton band) to ∼100 cm−1 at 700 nm and finally reaches a value of ∼0.30 cm−1 at λ∼1.3 μm for polarization parallel to the chain axis. Above λ∼1050 nm, the absorption coefficient becomes polarization independent. The low nonresonant absorption coefficient as measured is desirable in terms of nonlinear optical device applications of this material.
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78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
42.70.-a Optical materials
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