Optical properties of In/sub 0.8/Ga/sub 0.2/As self-assembled quantum dots on SiO/sub 2/-patterned [001] vicinal GaAs substrates
In this study, we investigated the optical properties of InGaAs SAQD on SiO/sub 2/-patterned exact and 5 /spl deg/-off [001] GaAs substrates. Also, we compared the discrete nature of the density of states in SAQDs for both starting materials.
Fabrication of single- or double-row aligned self-assembled quantum dots by utilizing SiO2-patterned vicinal (001) GaAs substrates
We investigated the formation of In0.8Ga0.2As self-assembled quantum dots (SAQDs) grown on SiO2-patterned 1°, 2°, and 5°-off (001) GaAs substrates by selective area metalorganic vapor phase epitaxy technique. The SiO2 patterns were filled with various stripe opening windows along the misorientation direction of the substrates. During the growth of the GaAs buffer layer on the opening regions, the steps on the (001) top facet was affected by the widths of the (001) top facet and the misorientation angles of the substrates. Single- or double-row aligned In0.8Ga0.2As SAQDs having definite interval were successfully fabricated on the (001) top facet with optimized top width and periodicity of step bunching. These results indicate that the selective growth technique of SAQDs by utilizing SiO2-patterned vicinal substrates is promising for nanoelectronic device applications such as single-electron memory devices.
New Low-Profile Applicators for Local Heating of Tissues
A new type of low-profile applicator is described giving efficient power transfer to tissue with low leakage. It consists of a resonant element spaced from a ground plane by low-loss material having high relative permittivity and some relative permeability. This combination is covered by similar material which can be placed in direct contact with the tissue to be heated, or separated from it by a water bolus as required. Laboratory measurements using phantom materials show that these applicators are well matched and produce well defined and relatively uniform heating profiles. Applicators having maximum dimensions of 3-15 cm covering the frequency range 1000-100 MHz, respectively, are described. Penetration depths of at least 4 cm at 100-200 MHz are achieved. Tests on anesthetised pigs and some clinical assessment have confirmed the usefulness of this compact low-frequency type of applicator and have shown that performance compares favorably with that of other recently reported types. The design can be optimized for treatment of specific sites, and suitable choice of dimensions and electrical characteristics of the layer material allow the low-profile concept to be extended over a wide range of operating frequencies.