Volume 91, Issue 4, 15 February 2002
Index of content:
Two-dimensional lateral superlattices of nanostructures: Nonlithographic formation by anodic membrane template91(2002); http://dx.doi.org/10.1063/1.1433173View Description Hide Description
A nonlithographic technique that utilizes highly ordered anodized aluminum oxide porous membrane as template is presented as a general fabrication means for the formation of an array of vastly different two-dimensional lateral superlattices structures. Hexagonal close-packed nanopore arrays were fabricated on Si, GaAs, and GaN substrates via reactive ion etching.Quantum dot arrays of various metals and semiconductors were formed through evaporation and subsequent etching. The two-dimensional lateral superlattice structures fabricated using this method are of a high level of ordering, uniformity, and packing density. The diameter and periodicity of the nanostructures are determined by the features of the original alumina membrane, which can be adjusted by varying the anodization conditions.
Measurement of the sheet resistance of resistive films on thin substrates from 120 to 175 GHz using dielectric waveguides91(2002); http://dx.doi.org/10.1063/1.1430534View Description Hide Description
A method is reported for the measurement of the sheet resistance, at microwave frequencies, of conducting films supported on thin dielectric substrates. The sheet resistance is found from measurements of the millimeter-wave power transmission through the film using a millimeter-wave source and power meter coupled through dielectric waveguides. The accuracy of this technique does not depend on the precise placement of the waveguide terminations with respect to the substrate, in contrast to methods using metallic waveguides or coils. This method is used to characterize the sheet resistance of semiconductor samples in the frequency range 120–175 GHz and the results are compared to the dc values obtained by conventional techniques. Sheet resistance values can be easily measured by this method in the range from 1 to 1000 Ω.
91(2002); http://dx.doi.org/10.1063/1.1435412View Description Hide Description
Largely tunable midinfrared (8–12 μm) generation is obtained in GaAs and ZnSe slabs by difference frequency mixing of optical parametric oscillator output waves (∼2 μm). The coherence lengths determined in semiconductor wedges are in excellent agreement with estimates from known Sellmeir formulas.
Effective mass and exciton binding energy in ordered (Al)GaInP quantum wells evaluated by derivative of reflectivity91(2002); http://dx.doi.org/10.1063/1.1436553View Description Hide Description
Low-temperature (1.8 K) magneto-opticalreflectivity spectroscopy together with derivative operation has been employed in evaluating the reduced effective mass and exciton binding energy in quantum wells(QWs). Low uncertainty of the method in identifying excitonic transition energy meV) enables a simultaneous determination of both the heavy-hole (hh) and light-hole (lh) excitons in the QWs with ordering. The obtained effective masses manifest to be ordering-dependent, the dependence of which is compared with that reported for the bulk material. Results from the lattice-matched QWs suggest that the magnetic-field enhancement of the oscillator strength is stronger for the hh exciton than for the lh exciton.