Scanning thermal imaging by near-field fluorescence spectroscopy

A scanning thermal microscope that uses a fluorescent particle as a temperature probe has been developed. The particle, made of a rare-earth ion-doped fluoride glass, is glued at the extremity of a sharp tungsten tip and scanned on the surface of an electronic device. The temperature of the device is determined by measuring the fluorescence spectrum of the particle at every point on the surface and by comparing the intensity variations of two emission lines. As an example, we will show some images obtained on a nickel stripe 1 mu m wide, heated by an electrical current. A good agreement is observed with a simulation of the temperature field on the device.