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  • 1
    Electronic Resource
    Electronic Resource
    Practical aspects of Kelvin probe force microscopy (1999)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 70 (1999), S. 1756-1760 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We discuss practical aspects of Kelvin probe force microscopy (KFM) which are important to obtain stable images of the electric surface potential distribution at high spatial resolution (〈100 nm) and high potential sensitivity (〈1 mV) on conducting and nonconducting samples. We compare metal-coated and semiconducting tips with respect to their suitability for KFM. Components of the metal coating can become detached during scanning, introducing sudden offset jumps in the potential maps (typically up to 350 mV between adjacent scan lines). However, n-doped silicon tips show no substantial tip alterations and, therefore, provide a stable reference during the experiment (offset jumps typically up to 40 mV between adjacent scan lines). These semiconducting tips must be electrically connected via contact pads. We use InGa and colloidal silver pads which are easily applied to the substrate supporting the cantilever and have a low enough differential contact resistance (350 Ω and 2.2 kΩ, respectively). Furthermore, we introduce a simple procedure to fine tune the feedback which detects the electric surface potential and show how the basic KFM setup has to be modified to gain access to the necessary control signals. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1149664
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  • 2
    Electronic Resource
    Electronic Resource
    Oxygen vacancy ordering in epitaxial La0.5Sr0.5CoO3−∂ thin films on (001) LaAlO3 (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 90 (2001), S. 3319-3324 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: High-resolution transmission electron microscopy (HRTEM), electron energy-loss spectroscopy (EELS), and electron diffraction were used to study the microstructure of epitaxial La0.5Sr0.5CoO3−∂ thin films grown on (001) oriented LaAlO3 substrates. Films were characterized before and after annealing treatments under different oxygen partial pressures. EELS shows that annealing reduces the valence state of cobalt due to loss of oxygen. HRTEM image simulations show that the superstructure contrast observed in HRTEM can be explained by shifts of cations in planes containing ordered oxygen vacancies. The as-deposited film showed weak, short-range ordering of oxygen vacancies within nanometer-sized domains. The annealed film showed long-range order and a strong anisotropy in ordering, with the oxygen-deficient planes aligned parallel to the film/substrate interface. We propose that the anisotropy in ordering is a mechanism of stress relief in these films. Implications of the observed microstructure on the oxygen transport and surface oxygen exchange properties are discussed. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1401793
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  • 3
    Electronic Resource
    Electronic Resource
    Reactions of Y2O3 films with (001) Si substrates and with polycrystalline Si capping layers (2002)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 81 (2002), S. 712-714 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We use electron energy-loss spectroscopy in scanning transmission electron microscopy to investigate interfacial reactions of chemical vapor deposited Y2O3 films with the Si substrate and with in situ polycrystalline Si ("poly-Si") capping layers after postdeposition annealing. We find that in situ capping layers significantly reduce the formation of SiO2 at the interface with the substrate, but silicates form at the substrate and the capping layer interfaces. Predeposition nitridation of the Si surface can impede the reaction at the substrate interface, resulting in crystallization of Y2O3 in the film interior. Possible mechanisms of the silicate formation are discussed. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1496500
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  • 4
    Electronic Resource
    Electronic Resource
    Interaction of iron with a grain boundary in boron-doped multicrystalline silicon (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 77 (1995), S. 3725-3728 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The article presents a study of the interaction of iron with a grain boundary in boron-doped multicrystalline silicon. The sample was intentionally contaminated with iron to a few 1014 cm−3 and investigated by the electron-beam-induced-current technique (measurement of minority-carrier diffusion length, quantitative imaging) in the temperature range 80–300 K. The measurements were carried out for two different states of iron in the sample: (i) iron paired with boron, i.e., as FeB, and (ii) iron as interstitial iron Fei. The differences between diffusion lengths for these two states were used to estimate the iron concentration. The analysis of the data revealed a pronounced iron profile around the grain boundary, indicating gettering of about 4×1011 iron atoms per cm2. The recombination velocity of the grain boundary is about 5×105 cm s−1 at 300 K and is not changed by the FeB destruction treatment. The temperature dependence of the iron-related diffusion length components is discussed and found to be in satisfactory agreement with what is expected from Shockley–Read–Hall theory. Further, the diffusion length analysis revealed also a strong recombination channel of unidentified origin. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.358611
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  • 5
    Electronic Resource
    Electronic Resource
    Microstructure of epitaxial Pb(Mg1/3Nb2/3)O3–PbTiO3 thin films grown by metalorganic chemical vapor deposition (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 3526-3531 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Epitaxial, perovskite Pb(Mg1/3Nb2/3)O3–PbTiO3 films were grown by metalorganic chemical vapor deposition under various deposition conditions and characterized by x-ray diffraction and transmission electron microscopy. Pyrochlore free films were obtained under all deposition conditions used in this study. Magnesium-rich growth conditions lead to the formation of a Mg-rich impurity phase in the films, embedded as coherent lamellae parallel to the growth direction. Depending on the growth conditions, a wide variation in the stoichiometry and volume fraction of this impurity phase was found between samples, whereas morphology and crystal structure were found to be very similar. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.372376
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  • 6
    Electronic Resource
    Electronic Resource
    Subwavelength-sized aperture fabrication in aluminum by a self-terminated corrosion process in the evanescent field (2002)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 80 (2002), S. 3397-3399 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We present a simple, one-step process to fabricate apertures of high quality for scanning near-field optical microscope probes based on aluminum-coated silicon-nitride cantilevers. An evanescent optical field at the glass–water interface is used to heat up the aluminum at the tip apex due to light absorption. The heat induces breakdown of the passivating oxide layer and corrosion of the metal. Apertures with a protruding silicon-nitride tip of up to 30 nm height and minimal diameter of 38 nm are fabricated. The diameter is predefined by the lateral dimension of the silicon-nitride tip while the tip height is controlled by the penetration depth of the evanescent field. The corrosion process proves to be self-terminating, yielding highly reproducible tip heights. Near-field optical resolution in the transmission mode of 85 nm is demonstrated. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1476059
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  • 7
    Electronic Resource
    Electronic Resource
    Oxidation states of titanium in bulk barium titanates and in (100) fiber-textured (BaxSr1−x)Ti1+yO3+z thin films (2001)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 79 (2001), S. 3149-3151 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Chemical shifts of titanium L edges and oxygen K edges in electron energy-loss spectroscopy in transmission electron microscopy were used to detect valence state reduction of Ti in bulk barium titanates, used as reference materials, and in (BaxSr1−x)Ti1+yO3+z (BST) thin films grown with excess Ti. A hollandite-type Ba titanate, containing Ti with an average valence state of approximately 3.7 in octahedral coordination, showed large chemical shifts relative to rutile TiO2 and BaTiO3, containing only Ti4+. In BST, chemical shifts relative to BaTiO3 were measured from grain interiors of columnar films with different amounts of excess Ti. We found that shifts, corresponding to an average valence state of Ti smaller than nominal 4+, increase with increasing amounts of excess Ti in the films. The results show that at least some amount of excess Ti is accommodated in these films by a defect mechanism that requires a reduction of the average valence state of Ti. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1418036
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  • 8
    Electronic Resource
    Electronic Resource
    Accommodation of nonstoichiometry in (100) fiber-textured (BaxSr1−x)Ti1+yO3+z thin films grown by chemical vapor deposition (1999)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 74 (1999), S. 2432-2434 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have investigated the microstructural accommodation of nonstoichiometry in (BaxSr1−x)Ti1+yO3+z thin films grown by chemical vapor deposition. Films with y=0.04 and y=0.15 were studied by high-spatial resolution electron energy-loss spectroscopy, revealing changes in chemistry and local atomic environment both at grain boundaries and within grains as a function of titanium content. We find that excess titanium in the samples with y=0.15 segregates to the grain boundaries in addition to being partially accommodated in the grain interior. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.123871
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  • 9
    Electronic Resource
    Electronic Resource
    Structure and stability of La2O3/SiO2 layers on Si(001) (2001)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 79 (2001), S. 102-104 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: High-resolution transmission electron microscopy and electron energy-loss spectroscopy (EELS) were used to investigate La2O3/SiO2/Si structures. The La2O3 layers were deposited on thermal SiO2 on silicon, followed by rapid thermal annealing treatments at 600 °C and 800 °C in a nitrogen ambient. After annealing at 600 °C, the oxide layers were amorphous. After an 800 °C treatment, crystallites appeared in the original La2O3 layer, and the total oxide layer thickness increased by 17%, most likely due to the oxygen diffusion and reaction at the Si/SiO2 interface. EELS, using a 0.2 nm probe, showed that rapid thermal annealing at 600 °C did not cause significant La diffusion into the SiO2 layer, whereas some intermixing was observed at 800 °C. We use the observed microstructures to estimate equivalent oxide thicknesses. The results demonstrate that oxygen partial pressures and initial SiO2 thickness need to be carefully controlled to control SiO2 formation at the Si interface and to achieve target equivalent oxide thickness. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1383268
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  • 10
    Electronic Resource
    Electronic Resource
    Investigation of the cleaved surface of a p–i–n laser using Kelvin probe force microscopy and two-dimensional physical simulations (2000)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 76 (2000), S. 2907-2909 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have investigated the cross-sectional electric field and potential distribution of a cleaved n+-InP/InGaAsP/p+-InP p–i–n laser diode using Kelvin probe force microscopy (KFM) with a lateral resolution reaching 50 nm. The powerful characterization capabilities of KFM were compared with two-dimensional (2D) physics-based simulations. The agreement between simulations and KFM measurements regarding the main features of the electric field and potential is very good. However, the KFM yields a voltage drop between n- and p-doped InP regions which is 0.4 times the one simulated. This discrepancy is explained in terms of surface traps due to the exposure of the sample to the air and in terms of incomplete ionization. This hypothesis is confirmed by the 2D simulations. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.126513
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