In this paper we present an experimental and theoretical study of the thermoreflectance response as a function of the probe wavelength for layered microelectronics structures. The investigated sample consists of a polycrystalline silicon conducting track grown on a SiO2-coated Si substrate. Thermoreflectance measurements were carried out in the wavelength range from 450to750nm with the track biased in modulated regime. An oscillating pattern is observed in the spectral region where the upper layer is transparent. Such oscillations are due to the interference resulting from the multiple reflections at the interfaces. Using a thermo-optical model, we show that the optical constants (n and k) of the materials, which are wavelength dependent, as well as their temperature derivatives (dn∕dT and dk∕dT), strongly influence the thermoreflectance signal. The optical thicknesses of the layers, mainly determined by the real part of the refractive indices, define the period of oscillation. On the other hand, the imaginary part of the refractive indices establishes the cutoff wavelength of the oscillations. Below this cutoff wavelength, the probe light does not penetrate the material and the upper-surface reflectance dominates the signal.

No abstract

Time-resolved Z-scan measurements were performed in a Nd 3+ -doped Sr 0.61 Ba 0.39 Nb 2 O 6 laser crystal through ferroelectric phase transition. Both the differences in electronic polarizability ͑⌬␣ p ͒ and cross section ͑⌬͒ of the neodymium ions have been found to be strongly modified in the surroundings of the transition temperature. This observed unusual behavior is concluded to be caused by the remarkable influence that the structural changes associated to the ferro-to-paraelectric phase transition has on the 4f → 5d transition probabilities. The maximum polarizability change value ⌬␣ p = 1.2ϫ 10 −25 cm 3 obtained at room temperature is the largest ever measured for a Nd 3+ -doped transparent material.

We investigated the effect of electrostatic discharge on n-channel metal-oxide-semiconductor field-effect transistors using the thermoreflectance microscopy. The gate terminals of the transistors were submitted to electrostatic pulses on a zap system that respects the human body model. The pulse intensity varied from 40to140V in a cumulative sequence. Electrical characterization showed that the transistor threshold voltage was no longer positive for pulses of 110V and higher. No significant changes in the thermoreflectance maps were observed in these cases. For pulses of 140V a large leakage current appeared, and the thermoreflectance maps revealed strong peaks (localized spot) associated with the induced damage.