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  • 1
    Electronic Resource
    Electronic Resource
    Structural, electrical, and optical properties of SnO2 nanocrystalline thin films grown on p-InSb (111) substrates (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 90 (2001), S. 175-180 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: SnO2 thin films were grown on p-InSb (111) substrates by radio-frequency magnetron sputtering at low temperature. Atomic force microscopy images showed that the root mean square of the average surface roughness of the SnO2 films grown on the InSb (111) substrates with an Ar/O2 flow rate of 0.667 and at a temperature of 200 °C had a minimum value of 2.71 nm, and x-ray diffraction and transmission electron microscopy (TEM) measurements showed that these SnO2 thin films were polycrystalline. Auger electron spectroscopy and bright-field TEM measurements showed that the SnO2/p-InSb(111) heterointerface was relatively abrupt. High-resolution TEM measurements revealed that the SnO2 films were nanocrystalline and that the grain sizes of the nanocystalline films were below 6.8 nm. The capacitance–voltage measurements at room temperature showed that the type and the carrier concentration of the nominally undoped SnO2 film were n type and approximately 1.67×1016 cm−3, respectively, and the current–voltage curve indicated that the Au/n-SnO2/p-InSb diode showed tunneling breakdown. Photoluminescence spectra showed that peaks corresponding to the donor acceptor pair transitions were dominant and that the peak positions did not change significantly as a function of the measured temperature. These results indicate that the SnO2 nanocrystalline thin films grown on p-InSb (111) substrates at low temperature hold promise for new kinds of potential optoelectronic devices based on InSb substrates, such as superior gas sensors and high-efficiency solar cells. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1372159
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  • 2
    Electronic Resource
    Electronic Resource
    Existence of a CuAu–I-type ordered structure in lattice-mismatched InxGa1−xAs/InyAl1−yAs multiple quantum wells (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 2503-2505 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Selected area electron diffraction pattern (SADP) and transmission electron microscopy (TEM) measurements were carried out to investigate the ordered structures in lattice-mismatched InxGa1−xAs/InyAl1−yAs multiple quantum wells (MQWs). The SADP showed two sets of extra spots with asymmetrical intensity, and the high-resolution TEM image showed doublet periodicity in the contrast of the (001) lattice planes. The results of the SADP and the TEM measurements showed that a CuAu–I-type ordered structure was observed near the lattice-mismatched InxGa1−xAs/InyAl1−yAs heterointerfaces. This CuAu–I-type ordered structure had an antiphase boundary in the periodically regular InxGa1−xAs/InyAl1−yAs lattice-mismatched region. The existence of a CuAu–I-type ordered structure in InxGa1−xAs/InyAl1−yAs MQWs might originate from the lattice mismatch between the InxGa1−xAs and the InyAl1−yAs layers. These results provide important information on the microstructural properties for improving operating efficiencies in long-wavelength optoelectronic devices, such as strain compensated electroabsorption modulators utilizing lattice-mismatched InxGa1−xAs/InyAl1−yAs MQWs. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1337917
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  • 3
    Electronic Resource
    Electronic Resource
    Strain effects in lattice-mismatched InxGa1−xAs/InyAl1−yAs coupled double quantum wells (1998)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 73 (1998), S. 61-63 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Transmission electron microscopy (TEM) and Raman scattering spectroscopy measurements were performed to investigate strain effects in lattice-mismatched InxGa1−xAs/InyAl1−yAs modulation-doped coupled double quantum wells. The high-resolution TEM images showed that a 100-Å In0.8Ga0.2As deep quantum well and a 100-Å In0.53Ga0.47As shallow quantum well were separated by a 30-Å In0.25Ga0.75As embedded potential barrier. The selected-area electron-diffraction pattern obtained from TEM measurements on the InxGa1−xAs/InyAl1−yAs double quantum well showed that the InxGa1−xAs active layers were grown pseudomorphologically on the InP buffer layer. The values of the strain and the stress of the InxGa1−xAs layers were determined from the electron-diffraction pattern. Based on the TEM results, a possible crystal structure for the InxGa1−xAs/InyAl1−yAs coupled double quantum well is presented. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.121723
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  • 4
    Electronic Resource
    Electronic Resource
    Magnetotransport, magneto-optical, and electronic subband studies in InxGa1−xAs/InyAl1−xAs modulation-doped strained double quantum wells (1997)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 82 (1997), S. 4388-4393 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Magnetotransport and magneto-optical measurements on InxGa1−xAs/InyAl1−yAs modulation-doped strained double quantum wells with a 100 Å In0.8Ga0.2As well and a 100 Å In0.53Ga0.47As quantum wells separated by a 35 Å In0.25Ga0.75As potential barrier were carried out to investigate the electrical and the optical properties of the electron gas in the quantum wells. The Shubnikov-de Haas measurements at 1.5 K demonstrated clearly the occupation of three subbands in the quantum wells by a two-dimensional electron gas. The electron effective masses determined from the slopes of the cyclotron resonance peak energies as a function of the magnetic field were 0.06171 and 0.05228me. The electronic subband energies, the subband energy wavefunctions, and the Fermi energy in the quantum wells were self-consistently calculated a transfer matrix method taking into account the exchange-correlation effect, the strain effect, and the nonparabolicity effect, and the results of the cyclotron resonance measurements qualitatively show the nonparabolicity effect in the strained double quantum well. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.366165
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  • 5
    Electronic Resource
    Electronic Resource
    Electronic parameters of the two-dimensional electron gas in modulation-doped single quantum wells due to an embedded deep step layer (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 2649-2652 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The Shubnikov–de Haas (S–dH) measurements at 1.5 K clearly demonstrated the existence of a two-dimensional electron gas (2DEG) in the modulation-doped Al0.25Ga0.75As/InyGa1−yAs/GaAs single and step quantum wells, and the fast Fourier transformation results for the S–dH data clearly indicated the electron occupation of one subband in the asymmetric single and step quantum wells. While the electron carrier density of the 2DEG in the step quantum well was larger than that in the single quantum well due to the larger conduction-band discontinuities, the mobility of the 2DEG in the step quantum well was smaller than that in the single quantum well because of the interface scattering resulting from the embedded step well. The electron effective mass in the step quantum well was smaller than that in the single quantum well, which was consistent with a smaller mass of the embedded deep step layer. The electronic subband energy, the energy wave function, and the Fermi energy in the InyGa1−yAs step quantum wells were calculated by using a self-consistent method taking into account exchange-correlation effects together with strain and nonparabolicity effects. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1344222
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  • 6
    Electronic Resource
    Electronic Resource
    Microstructural, electrical, and optical properties of SnO2 nanocrystalline thin films grown on InP (100) substrates for applications as gas sensor devices (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 88 (2000), S. 3759-3761 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: SnO2 thin films were grown on p-InP (100) substrates by using radio-frequency magnetron sputtering at low temperature. Transmission electron microscopy (TEM) and electron diffraction pattern measurements showed that these SnO2 thin films were nanocrystalline. The capacitance–voltage measurements at room temperature showed that the type and the carrier concentration of the nominally undoped SnO2 film were n type and approximately 1.62×1016 cm−3, respectively. Raman scattering measurements showed that the grain sizes of the nanocrystalline films were below 10 nm, which was in reasonable agreement with the result obtained from the high-resolution TEM measurements. Photoluminescence measurements showed a broad peak below the band-to-band emission. These results can help improve the understanding of SnO2 nanocrystalline films grown on p-InP (100) substrates for applications in high-sensitivity gas sensors. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1288021
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  • 7
    Electronic Resource
    Electronic Resource
    Electronic property variations due to an embedded potential barrier layer in modulation-doped step quantum wells (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 5089-5092 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Electronic property variations of a two-dimensional electron gas (2DEG) in modulation-doped step quantum wells due to an embedded potential barrier were studied by performing Shubnikov–de Haas (SdH), Van der Pauw–Hall-effect, and cyclotron resonance measurements on two kinds of InxGa1−xAs/InyAl1−yAs step quantum wells which were one without and the other with an embedded barrier. The fast Fourier transformation results for the SdH data at 1.5 K indicated the electron occupation of two subbands in both step quantum wells. The total electron carrier density and the mobility of the 2DEG in the step quantum well with an embedded barrier were smaller than those in the quantum well without an embedded barrier. The electron effective masses were determined from the slopes of the main peak absorption energies as functions of the magnetic field, and satisfied qualitatively the nonparabolicity effects in both quantum wells. The electronic subband energies, the wave functions, and the Fermi energies were calculated by using a self-consistent method taking into account exchange-correlation effects together with strain and nonparabolicity effects. These present results indicate that the electronic parameters in modulation-doped InxGa1−xAs/InyAl1−yAs step quantum wells are significantly affected by an embedded barrier. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1454198
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  • 8
    Electronic Resource
    Electronic Resource
    Microstructural and electronic properties of Ni thin films grown on p-InP (100) substrates (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 4238-4241 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Ion beam-assisted deposition of Ni on p-InP (100) at room temperature was performed in order to produce Ni thin films with high quality and Ni/p-InP (100) heterostructures with abrupt heterointerfaces. An atomic force microscopy image showed that the root mean square of the average surface roughness of the Ni film was 21.3 Å, and x-ray diffraction and transmission electron microscopy (TEM) measurements show that Ni film layers grown on InP (100) substrates were polycrystalline. Auger electron spectroscopy and TEM measurements showed that Ni films grown on p-InP (100) substrates at room temperature had no significant interdiffusion problems. The work function of the Ni thin film was determined from the secondary electron emission coefficients obtained with a focused ion beam. These results provide important information on the microstructural and electronic properties for Ni thin films grown on p-InP (100) substrates at room temperature. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1454196
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  • 9
    Electronic Resource
    Electronic Resource
    Coalescence and electron activation energy in CdTe/ZnTe nanostructures (2002)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 81 (2002), S. 487-489 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Atomic force microscopy (AFM) and photoluminescence (PL) measurements were carried out to investigate the coalescence and electron activation energy in CdTe/ZnTe nanostructures. The results of the AFM images show that uniform CdTe quantum dots (QDs) are formed and that the transformation from CdTe QDs to CdTe quantum wires is caused by the coalescence. The excitonic peaks corresponding to the transition from the ground electronic subband to the ground heavy-hole band in the CdTe/ZnTe QDs shifted to higher energy in comparison with those of the CdTe/ZnTe quantum wires. The activation energy of the electrons confined in the CdTe QDs, as obtained from the temperature-dependent PL spectra, was higher than those in CdTe quantum wells and quantum wires. The present results can help to improve the understanding of coalescence and electron activation energy in CdTe/ZnTe nanostructures. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1490634
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  • 10
    Electronic Resource
    Electronic Resource
    Microstructural and optical properties of SnO2 thin films grown on heavily doped n-InP(100) substrates (2001)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 79 (2001), S. 2187-2189 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Bright-field transmission electron microscopy (TEM) and high-resolution TEM images and an electron diffraction pattern showed that the SnO2 layers grown on heavily doped n-InP(100) substrates were nanoscale thin films. X-ray photoelectron spectroscopy showed that the positions of the peaks corresponding to the Sn 3d5/2, the Sn 3d3/2, and the O 1s levels for the SnO2 thin film were slightly shifted toward the lower energy side in comparison with those for bulk SnO2. The refractive indices obtained by spectroscopic ellipsometry were above 2.2 around the SnO2 energy gap of the SnO2 thin films. The maximum intensity of the optical transmittance for the SnO2 nanoscale thin film with 3939 Å thickness was above 90%. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1403663
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