Nanosized Thin Films Surface Effects in Standard Calorimetry Using Low Laser Intensity: Experiment Versus Theory
M. Oane, A.M. Bucă, I.N. Mihăilescu and C.M. Ticoş
In the present work we investigated the thermal field distributions obtained by low intensity laser irradiation of layers with variable sizes: from nano to bulk size. We selected Fe as bulk materials and Au for the underlying material with variable size at nano-scale. We find out a method in order to decrease the sample temperature: to put between the Fe bulk surface and incident laser beam a nanoscale Au thin film. On the other hand, we can choose to irradiate the face of Fe bulk, especially when we have a much unpolished Fe surface, which leads us to an increase of the total bulk thermal field. The mathematical models based on the Green function and integral transform technique where employed. The main conclusion is that at low laser intensity in the ultraviolet (UV) range using the proposed method we can decrease the thermal fields with about 10 to 15%. We choose the scale of study to be 20 to 500 nm because 20 nm is the lower limit of Fourier equation validity and 500 nm is the upper limit like theoretical definition of nanoscale materials. The experiment data are in concordance with our theoretical predictions and other data from literature. From theoretical point of view, we obtain an analogue equation for the temperature variation of the nanosized thin film–bulk metal system in ‘comparison’ with the simple bulk metal situation. It is important to mention from the very beginning that we are dealing with nanosized materials and not with nanomaterials. Only the scale of the materials changes in an important way the heat conduction.
Keywords: Ultraviolet (UV) laser, low intensity irradiation, nanoscale, thermal field distributions, Green function method, integral transform technique