Peak Energy Ep Research Articles

Investigation of monolayer roughness in HgTe-CdTe superlattices

Infrared photoluminescence (PL) measurements were performed on (2ID-oriented superlattices with energy gaps in the range 110–495 meV. Most of the samples with thinner HgTe quantum wells displayed two PL peaks separated by Δhω ≈ 30–65 meV (which generally increased with decreasing well thickness). Both peak energies (Ep) sometimes varied gradually with location on the surface, and in one case three peaks of approximately equal spacing were observed in some locations. The data are consistent with a model which assumes the presence of randomly distributed islands having well thicknesses varying by approximately one monolayer. We find that Ahco and the variations of the spectra with temperature agree well with calculations based on this simple model.

Optical Characterization of Undoped a-Si:H Prepared by Photo-CVD and GD Techniques

We have optically characterized undoped a-Si:H films prepared by photo-CVD and GD techniques under various deposition conditions. Photoluminescence(PL) and transmission spectra were measured at 77 K, from which the peak energy Ep of the main PL band and the optical absorption edge Egopt could be deduced. We have obtained the Urbach energy E0 by means of photothermal deflection spectroscopy(PDS) at room temperature. The differences ΔE between Ep and Egopt were plotted against E0 for films prepared under various conditions, from which it was found that the same linear relation holds between ΔE and E0 commonly for films prepared by both techniques. We conclude that the increase of ΔE in films deposited at a low substrate temperature is mainly caused by a broadening of the tail states owing to disorder in the amorphous network.

Quantitative non‐destructive in‐depth composition information from XPS

AbstractThe XPS peak shape from inhomogeneous transition metals is studied theoretically under variation of the path length R travelled by the photoelectron in the solid, the XPS peak energy Ep, and the particular metal M. The variation in peak shape is characterized by a single parameter D = Ap/B which is the ratio of the peak area to the increase in background signal 30 eV below the peak energy. It is found that D is a strong function of R, a moderate function of Ep and to first order independent of M. This gives theoretical support to the idea suggested previously of using D for fast non‐destructive extraction of in‐depth composition information. To a good approximation we have D(R,Ep) = (425+Ep) × R, with Ep in eV, R in Å and D(R,Ep) in eV. The practical use of this function in the analysis of experimental data is discussed.

Accurate electron probe determination of aluminum composition in (Al, Ga)As and correlation with the photoluminescence peak

The composition of Alx Ga1−xAs has been measured with improved accuracy by electron probe microanalysis using an aluminum-copper alloy standard rather than an elemental aluminum standard. Details of the experimental procedure are given. A calibration curve, relating the photoluminescence peak energy (Ep) to aluminum concentration (x), has been obtained. A least-squares fit to the data gives Ep(eV)=1.42+1.45x−0.25x2 for 0<x≤0.45.