Advances in thermal wave based microscopy

Abstract

The recent advances in thermal wave based microscopy comprising optical beam and near field techniques are discussed. A novel method is described which relies on the simultaneous optical and electrical excitation of the thermo-reflectance signal allowing to image depletion regions of the electron gas in the neighbourhood of insulating lines in a semiconductor device. Here the signal is detected at multiples of the excitation frequencies. A combined scanning thermal and scanning thermo-elastic microscope is presented, which has been applied to measure the temperature of hot areas in semiconductor transistors heated by a modulated current. The improvement towards a quantitative microscopy involves also simulations of the signals using finite elements calculations. New developments in the field of thermal wave ferromagnetic resonance microscopy based on the scanning thermal microscopes and scanning thermal expansion microscopes now offer a way to control of magnetic properties on nanometer scale. For Ni-dots grown on Au the local thermal expansion in the course of the microwave resonance absorption was measured as a function of the external magnetic field. A recently developed ferromagnetic resonance thermal wave microscope based on the local thermal modulation of the microwave resonance by a thermal AFM probe was first applied to image the lateral magnetic inhomogeneity of an iron film.