Signal production in scanning electron acoustic microscopy

Abstract

We have studied the variation of the electron acoustic signal in various materials as a function of the beam accelerating voltage and current. The results show that in most materials examined, e.g. copper, CuZnAl alloy and silicon, it is only the total incident beam power which determines the magnitude of the electron acoustic signal produced. In compensated GaAs the electron acoustic signal depends only on the beam current and is independent of the accelerating voltage which is unlike the case for highly doped GaAs which resembles the metals and silicon. Both semi-insulating and highly doped InP behave as the highly doped GaAs sample. The results are discussed in relation to some of the signal generation mechanisms thought to operate in the electron acoustic (or thermal wave) microscope.

Moment expansion of the linear density‐density response function

“…We refer to ref. [37] for a discussion of the computational scaling of the Lanczos-Sternheimer method compared to the conventional sum over states calculations.…”

“…The solution of the Dyson-like equation in the reduced dimension space of the moment expanded response function in analogy to ref. [37] is a possible extension of the presented change of representation. The shape of the Hartree exchange correlation Kernel, that is, an intramolecular interaction, might require high angular momentum contributions, which reduces the advantage of the moment expanded representation.…”

“…[33][34][35][36] Very recently, highly promising results for GW and RPA correlation energies have been achieved from explicit calculation of v s ðr; r 0 ; xÞ using Lanczos chains. [13,37] These techniques start from a diagonalization of the non-interacting static density-density response function, calculate its frequency dependence via Lanczos chains, and finally iterate the Dyson equation to obtain the interacting frequency dependent density-density response function.…”

“…The promising feature of this new Lanczos-based approach is the use of the eigenfunctions of the density-density response function as basis for subsequent calculations. [13,37] The conventional route via the sum-over-states expression in eq. (2) employs auxiliary bases via density fitting techniques.…”

Polarization Energies from Efficient Representation of the Linear Density–Density Response Function

“…The LDDRF is also important for the adiabatic‐connection fluctuation–dissipation theorem, symmetry adapted perturbation theory, [ 36–40 ] and the random phase approximation. [ 41–44 ]…”