Thermal properties study of silicon nanostructures by photoacoustic techniques

Abstract

The photoacoustic method with piezoelectric detection for the simultaneous evaluation of the thermophysical properties is proposed. The approach is based on the settling of an additional heat sink for redistribution of heat fluxes deposited on the sample surface. Firstly, the approach was tested on the porous silicon with welldefined morphology and well-studied properties. Then, heat capacity and thermal conductivity of silicon nanowires arrays have been investigated by recovering the experimental data through numerical simulations. The decrease of heat capacity and effective thermal conductivity of the samples upon increasing thickness and porosity of the sample is observed. Such behavior could be caused by the increase of the structure heterogeneity. In particular, this can be related to larger disorder (increased density of broken nanowires and larger porosity) that appears during the etching process of the thick layers.

In Situ Photoacoustic Study of Optical Properties of P-Type (111) Porous Silicon Thin Films

“…The solution in the time domain allows the calculation of the instantaneous PSi etching rate and thermal properties [ 13 ]. However, in this experimental configuration, light modulation frequency remains constant during the etching monitoring.…”

“…Then, it is possible to monitor and control the etching process using in situ techniques such as optical interferometry and photoacoustics [ 5 , 9 , 10 , 11 ]. Additionally, photoacoustics allows the characterization of the thermal properties of PSi structures and composites [ 12 , 13 , 14 , 15 ].…”

Photothermal Effects and Heat Conduction in Nanogranular Silicon Films

“…For example, n-type thick porous Si samples have multi-porous (nano, meso, micro) and p+, p-type samples have single porous morphologies [30]. In general, measured thermal conductivities (0.53 -0.19 W/mK ) of our Si nanogranular films are in the range of the lowest thermal conductivity values of nanostructurely voided Si films [29][30][31][32][33][34][35][36][37][38][39][40][41][42][43][44][45][46][47][48], Si nanowire films [53][54][55][56], amorphous porous Si films [49][50][51][52], crystalline porous Si membranes [57,58] and sin-Si NP tablets [24][25][26][27][28]. Additionally, when the size of a nanostructure becomes comparable or smaller than , phonons collide with intergranular boundaries much more often than in single crystalline bulk materials.…”

“…To the best of our knowledge, the thermal transport in drop-casted substrate-supported randomly packed Si nanogranular films with defined NP sizes and spherical shapes, have never been studied before compared to other various types of nanostructurally voided Si films ranging from low porosity pressure sintered nanostructured bulk Si (sint-Si) [24][25][26][27][28], crystalline porous Si (c-por-Si) [29][30][31][32][33][34][35][36][37][38][39][40][41][42][43][44][45][46][47][48], amorphous porous Si (a-por-Si) [49][50][51][52], crystalline porous Si nanowire (c-por-Si NW) films [53][54][55][56] to c-por-Si membranes [57,58]. As opposed to mainly top-down fabrication methods [29][30][31][32][33][34][35][36][37][38][39]…”

Optimized photoacoustic gas-microphone cell for semiconductor materials thermal conductivity monitoring

“…Among them are the impurities, dislocations [3], the influence of the different boundaries between the interfaces [4,5], the presence of the local elastic stresses [6], etc. [7,8]. Therefore, the quite fast and flexible diagnosis of thermal conductivity and related values is significant for studying the nature and checkup the behavior of semiconductor materials before and after various structure manipulations.…”