摘要:

We report a sensitive detection method for capacitive ultrasonic transducers. Detection experiments at 1.6 MHz reveal a minimum detectable displacement around2.5×10−4 Å/Hz.The devices are fabricated on silicon using surface micromachining techniques. We made use of microwave circuit considerations to obtain a good displacement sensitivity. Our method also eliminates the dependence of the sensitivity on the ultrasound frequency, allowing the method to be used at low audio frequency and static displacement sensing applications. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121506

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

The laser-induced breakdown spectroscopy technique has been extended to provide quantitative analysis of the mass and elemental composition of individual, submicrometer to micrometer-sized aerosol particles. A two-part approach was used for calibration of the overall mass concentration response, and of the characteristic plasma volume, equal to2.5×10−4cm3.Laboratory results are presented for submicrometer-sized particles containing a known concentration of magnetite. Additional data are presented for fine particulate matter measured in ambient air, including magnesium-containing particles with an average size of 313 nm. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121507

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

The microstructure of epitaxialSrRuO3thin films grown on vicinal (001)SrTiO3substrates with miscut angle of 1.9° and miscut direction of 12° away from [100] direction was studied using transmission electron microscopy (TEM). Cross-section as well as plan-view TEM studies revealed that these films are single domain with the in-plane epitaxial orientation relationship ofSrRuO3[001]//SrTiO3[010]andSrRuO3[1¯10]//SrTiO3[100].This result is in contrast to the previous studies of theSrRuO3thin films grown on exactly (001)SrTiO3,which are composed of two types of [110] domains with nearly the same volume fraction. The occurrence of these different domain structures is attributed to the step-flow growth of the film on the substrate surface due to the miscut. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121508

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

We have observed x-ray intensity oscillation fringes around low index Bragg reflections in aYBa2Cu3Ox(YBCO) thin film. By employing a combination of crystal truncation rod interference fringe measurements and x-ray reflectivity using synchrotron radiation, we have been able to probe the structures of highly oriented [001] YBCO grown on [001]SrTiO3substrates. The results demonstrate the presence of a thin disordered surface layer, the excellent coherence between the YBCO surface and the film-substrate interface, the presence of a small(3.2×10−4)interfacial strain existing in the YBCO film. This strain exists close to the film-substrate interface and extends approximately 300 Å into the micron-thick film. Our results demonstrate that high quality detailed information can be obtained, nondestructively, from thin film superconductors of thicknesses typically used for microwave and other applications. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121509

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

The equation of motion of a grazing impact oscillator is generalized to include compliant boundaries and impact energy dissipation, yielding the phase diagram, indentation and force. Good agreement with experimental results using tapping-mode atomic force microscopy is demonstrated. The relationship between phase and set-point amplitude is discussed in terms of the dissipation, showing that for a parameter space for which the system is highly nonlinear a chaotic response is possible. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121510

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Recent electron diffraction and microscopy studies of GaN nucleation layers have shown that faults in the stacking of the close-packed planes result in the coexistence of cubic and hexagonal phases within the layers. Using grazing incidence x-ray scattering, we have quantified the proportion of the cubic and hexagonal phases throughout the nucleation layer. We compare the structure of a 20 nm nucleation layer grown on sapphire by atmospheric pressure metal-organic chemical vapor deposition at525 °Cto that of an identical layer heated to1060 °C.The fractions of cubic and hexagonal phases in the layers are determined by a comparison of the scattering data with a Hendricks–Teller model. High temperature exposure results in a decrease of the cubic fraction from 0.56 to 0.17. The good agreement with the Hendricks–Teller model indicates that the positions of the stacking faults are uncorrelated. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121511

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

We have investigated as-grown sputtered films ofLa0.7Ca0.3MnO3in a thickness range between 5 and 200 nm onSrTiO3substrates. The films are epitaxial, strained, and smooth. All films order magnetically around 175 K. Very thin films show full magnetization at low temperatures, but the temperature of the metal–insulator transition is appreciably lower than the magnetic ordering temperature. In thick films, the magnetization is much lower than expected. Both effects are probably related to structural disorder as found by transmission electron microscopy. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121512

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Photoinduced structural change in hydrogenated amorphous silicon(a-Si:H)has been studied by a sensitive bending detection method using an optical lever. We observed thata-Si:Hfilms show not only thermal expansion due to a photothermal effect but also residual and persistent expansion after light soaking. The volume change is recovered by thermal annealing at 200 °C. A dehydrogenated sample annealed at 550 °C and a microcrystalline sample, in which photoinduced defects are not created, show little photoinduced expansion. The photoinduced expansion and photoinduced defect density show identical time evolution. These results suggest that the photoinduced expansion is related to the photoinduced defect creation. A quantitative evaluation of the photoinduced expansion indicates that the photoinduced structural change is spread over several molecular volumes around a photocreated defect. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121513

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Using an effective Hamiltonian parametrized from first principles, Monte Carlo simulations are performed in order to study the piezoelectric response ofBaTiO3in the ferroelectric tetragonal phase as a function of temperature. The effect of an electric field on the phase behavior is also illustrated by a simulation of the transformation of a rhombohedral domain into a tetragonal one under a strong field. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121514

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

The finite element method is applied to strain-induced islands. The distribution of the elastic energy in the island and the substrate is determined as a function of the island aspect ratio and inter-island distance. When the height-over-base ratio increases, the total elastic energy density decreases and the relative contribution of the substrate increases. When the inter-island distance decreases, the elastic energy density increases and the relative contribution of the substrate decreases. The influence of the aspect ratio on the relaxation rate is amplified for short inter-island distances. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121515

出版商:AIP    

年代:1998

数据来源: AIP