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1 Sep 2003

Volume 83, Issue 9, pp. 1689-1898

Issue Cover Spotlight Figure

Appl. Phys. Lett. 83, 1710 (2003); http://dx.doi.org/10.1063/1.1605792 (3 pages)

G. D. Chern, H. E. Tureci, A. Douglas Stone, R. K. Chang, M. Kneissl, and N. M. Johnson
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Transition from island formation to pseudomorphic growth in the submonolayer CdSe/ZnSe multilayer system

M. Kim, J. K. Furdyna, M. Dobrowolska, S. Lee, M. Cheon, and H. Luo

Appl. Phys. Lett. 83, 1728 (2003); http://dx.doi.org/10.1063/1.1605234 (3 pages) | Cited 1 time

Online Publication Date: 26 August 2003

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Transmission electron microscopy and photoluminescence measurements have been performed on samples with submonolayer (0.3 up to 0.9 ML) CdSe insertions in ZnSe in both single- and multilayer geometries. We observe a significant difference in Cd distribution in the layer plane between these two geometries for the same Cd coverage. While Cd-rich islands can be seen for a single layer of Cd, a layered growth is achieved in the multilayer samples. This effect is attributed to the reduction of lattice mismatch in the multilayer samples due to a high level of diffusion of Cd atoms along the growth direction. © 2003 American Institute of Physics.
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68.65.Cd Superlattices
81.05.Dz II-VI semiconductors
78.67.Pt Multilayers; superlattices; photonic structures; metamaterials
78.55.Et II-VI semiconductors
78.66.Hf II-VI semiconductors
68.37.Lp Transmission electron microscopy (TEM)

Mechanical characterization of trilayer thin films by the microbridge testing method

Wei-Hua Xu and Tong-Yi Zhang

Appl. Phys. Lett. 83, 1731 (2003); http://dx.doi.org/10.1063/1.1605799 (3 pages) | Cited 14 times

Online Publication Date: 26 August 2003

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Microbridge tests were conducted on two sets of trilayer samples, consisting of SiO2/Si3N4/SiO2 and Si3N4/SiO2/Si3N4, which were fabricated on 4 in. p-type (100) silicon wafers by means of the microelectromechanical fabrication technique. The experimental results were analyzed using the small deformation formula including substrate deformation. By changing the sample length, we determined the bending stiffness and the resultant residual force per unit width in each of the trilayer thin films. A simplification is proposed to estimate residual stress and Young’s modulus in each layer. Young’s moduli and residual stresses are estimated to be 54.59 GPa and −429.49 MPa for the silicon oxide films and 270.54 GPa and 550.75 MPa for the silicon nitride films, respectively. The microbridge testing method enables us to characterize the mechanical properties of each layer of sandwich-structured thin films. © 2003 American Institute of Physics.
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68.60.Bs Mechanical and acoustical properties
07.10.Cm Micromechanical devices and systems
81.70.Bt Mechanical testing, impact tests, static and dynamic loads
62.20.D- Elasticity
62.20.F- Deformation and plasticity

Isotopically enriched designer-diamond anvil

Paul A. Baker, Yogesh K. Vohra, Randolph S. Peterson, and Samuel T. Weir

Appl. Phys. Lett. 83, 1734 (2003); http://dx.doi.org/10.1063/1.1606877 (3 pages) | Cited 4 times

Online Publication Date: 26 August 2003

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Isotopically enriched (42 at. % 13C) designer-diamond anvils were grown by microwave plasma chemical vapor deposition using methane/hydrogen/oxygen chemistry. These isotopically enriched diamond layers can modify the thermal properties of the culet of high-pressure anvils and also allow the use of a 13C/12C Raman pressure sensor system for high-pressure, high-temperature measurements. Raman spectroscopy clearly revealed the isotopically mixed nature of the culet while the photoluminescence spectra at 80 K demonstrate the nitrogen-based defect center near the culet of the diamond anvil. The ability to isotopically modify the diamond culets offers yet another functionality for the embedded electric and magnetic sensors in a designer-diamond anvil. © 2003 American Institute of Physics.
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78.30.Hv Other nonmetallic inorganics
78.55.Hx Other solid inorganic materials
71.55.Ht Other nonmetals
81.05.U- Carbon/carbon-based materials

Exciton diffusion in light-emitting organic thin films studied by photocurrent spectra

C. L. Yang, Z. K. Tang, W. K. Ge, J. N. Wang, Z. L. Zhang, and X. Y. Jian

Appl. Phys. Lett. 83, 1737 (2003); http://dx.doi.org/10.1063/1.1606880 (3 pages) | Cited 20 times

Online Publication Date: 26 August 2003

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Photocurrent spectroscopy is employed to obtain the exciton diffusion coefficient and diffusion length in two typical light-emitting organic thin films, the hole transport material [N,N′-diphenyl-N,N′-bis(3-methyl-phenyl)-1,1′biphenyl-4,4′diamine] (TPD) and the electron transport material tris(8-hydroxyquinolinolato) aluminum III (Alq3). The photocurrent spectra of both films at higher biases exhibit either symbatic or antibatic responses. However, complicated responses are observed for smaller biases. At certain small biases, the direction of the photocurrent even alters with the energy of illuminating photons. A model based on exciton diffusion and dissociation at film/electrode interfaces is used to explain these experimental results. Good agreement is achieved between experiments and theory by taking into account both symbatic and antibatic responses, especially at zero or small biases. The diffusion coefficient and the diffusion length of excitons derived are 1.53×10−3 cm2 s−1 and 17 nm for TPD and 4×10−5 cm2 s−1 and 8 nm for Alq3, respectively. © 2003 American Institute of Physics.
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71.35.Cc Intrinsic properties of excitons; optical absorption spectra
78.66.Qn Polymers; organic compounds
73.50.Pz Photoconduction and photovoltaic effects

Temperature dependent spectroscopic studies of the electron delocalization dynamics of excited Ce ions in the wide band gap insulator, Lu2SiO5

E. van der Kolk, S. A. Basun, G. F. Imbusch, and W. M. Yen

Appl. Phys. Lett. 83, 1740 (2003); http://dx.doi.org/10.1063/1.1603337 (3 pages) | Cited 28 times

Online Publication Date: 26 August 2003

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Electron delocalization processes of optically excited states of Ce3+ impurities in Lu2SiO5 were investigated by means of a temperature and spectrally resolved photoconductivity study. By monitoring separately the strength of the photocurrent resulting from excitation into each of the Ce3+ 5d absorption bands, over a broad temperature region, three different delocalization processes, namely direct photoionization, thermal ionization, and tunneling, have been identified. The relative probabilities and temperature dependencies of each of these processes are discussed. The observed exponential temperature increase in the photocurrent, which spans six orders of magnitude, allows for the exact placement of the lowest energy 5d levels of the Ce3+ ions within the band gap. For Lu2SiO5:Ce3+, the lowest 5d state is determined to be 0.45 eV below the conduction band edge. © 2003 American Institute of Physics.
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71.55.Ht Other nonmetals
72.40.+w Photoconduction and photovoltaic effects
71.20.Ps Other inorganic compounds
72.20.Fr Low-field transport and mobility; piezoresistance

Heteroepitaxial growth of CuInS2 thin films on sapphire by radio frequency reactive sputtering

Y. B. He, W. Kriegseis, B. K. Meyer, A. Polity, and M. Serafin

Appl. Phys. Lett. 83, 1743 (2003); http://dx.doi.org/10.1063/1.1606505 (3 pages) | Cited 7 times

Online Publication Date: 26 August 2003

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Direct heteroepitaxial growth of uniform stoichiometric CuInS2 (CIS) thin films on sapphire (0001) substrates has been achieved by radio frequency reactive sputtering. X-ray ω–2θ scans reveal that the sputtered layers grow in a (112) orientation with a chalcopyrite structure. A rocking curve full width at half maximum of about 0.05° (180 arc sec) for the (112) peak demonstrates a nearly perfect out-of-plane arrangement of CIS (112)∥sapphire (0001). X-ray diffraction Phi scans further illustrate an excellent in-plane ordering of CIS [math10]∥sapphire (10math0). The sputtered thin CIS epilayers had a smooth surface with a typical root-mean-square roughness of about 3.3 nm as evaluated by atomic force microscopy. The epitaxial growth of tetragonal CIS on hexagonal sapphire provides evidence that heteroepitaxial growth may be realized between structures of different symmetry, such as films of cubic or tetragonal structures on hexagonal substrates or vice versa. © 2003 American Institute of Physics.
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68.55.-a Thin film structure and morphology
81.15.Cd Deposition by sputtering
68.35.Ct Interface structure and roughness
68.35.B- Structure of clean surfaces (and surface reconstruction)
68.37.Ps Atomic force microscopy (AFM)

Discontinuous tracks in relaxed Si0.5Ge0.5 alloy layers: A velocity effect

P. I. Gaiduk, A. Nylandsted Larsen, J. Lundsgaard Hansen, C. Trautmann, and M. Toulemonde

Appl. Phys. Lett. 83, 1746 (2003); http://dx.doi.org/10.1063/1.1605240 (3 pages) | Cited 8 times

Online Publication Date: 26 August 2003

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Strain-relaxed crystalline Si0.5Ge0.5 layers were irradiated with U ions of various energies (0.8–2.64 GeV) but of approximately identical electronic stopping power. Transmission electron microscopy reveals tracks of different morphology depending on the velocity of the projectiles. For decreasing beam energy, individual dotted defect structures form aligned discontinuous tracks including a large number of dislocation loops. No indication for track amorphization is found. © 2003 American Institute of Physics.
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61.80.Jh Ion radiation effects
61.85.+p Channeling phenomena (blocking, energy loss, etc.)
81.05.Hd Other semiconductors
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)
68.37.Lp Transmission electron microscopy (TEM)
61.82.Fk Semiconductors
61.72.Lk Linear defects: dislocations, disclinations

Morphology evolution during strained (In,Ga)As epitaxial growth on GaAs vicinal (100) surfaces

Z. M. Wang, J. L. Shultz, and G. J. Salamo

Appl. Phys. Lett. 83, 1749 (2003); http://dx.doi.org/10.1063/1.1606891 (3 pages) | Cited 15 times

Online Publication Date: 26 August 2003

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Molecular-beam-epitaxy growth of strained (In,Ga)As on GaAs vicinal (100) surfaces is investigated by scanning tunneling microscopy. Surface roughing as the consequence of step bunching driven by strain is explored. By tuning the In content over the range from 0.05 to 0.2, the step bunching is observed to exhibit considerable uniformity and order. These results experimentally demonstrate that strain-driven step bunching is a viable approach to provide templates for nanostructure growth. © 2003 American Institute of Physics.
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68.55.-a Thin film structure and morphology
81.05.Ea III-V semiconductors
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.37.Ef Scanning tunneling microscopy (including chemistry induced with STM)

Nanoheteroepitaxy of GaN on a nanopore array Si surface

J. Liang, S.-K. Hong, N. Kouklin, R. Beresford, and J. M. Xu

Appl. Phys. Lett. 83, 1752 (2003); http://dx.doi.org/10.1063/1.1604175 (3 pages) | Cited 37 times

Online Publication Date: 26 August 2003

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We report the growth by molecular beam epitaxy and the optical characterization of GaN films nucleated on a Si(111) surface that has been patterned by dry etching an ordered array of nanometer-scale pores prior to the growth. The etching is performed using an anodized aluminum oxide membrane as a mask. The nanopore array surface with the pore diameter of 60 nm and periodicity of 110 nm exhibits significant effects on emissivity and the optical properties of the resulting film. Room-temperature photoluminescence intensity increases by a factor of 5 for GaN grown on nanoporous Si. Peak shifts in photoluminescence and Raman spectroscopy suggest that the material grown on nanopores may be more relaxed than films grown on flat substrates. The effects of nanopore topography on the nucleation of GaN films offer a potential path to significant improvement of III-nitride heteroepitaxy for device applications. © 2003 American Institute of Physics.
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81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.55.-a Thin film structure and morphology
81.65.Cf Surface cleaning, etching, patterning
81.05.Ea III-V semiconductors
78.55.Cr III-V semiconductors
78.66.Fd III-V semiconductors
78.30.Fs III-V and II-VI semiconductors
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