Structural, Optical, and Thermal Analysis of n-Type Mesoporous Silicon Prepared by Electrochemical Etching

Abstract

International audienceMesoporous silicon (MePSi) is a promising material for future microelectronic chip multifunctionalization systems and for microsensing devices. In addition to the electrical characteristics, the thermal properties of MePSi layers affect the heat dissipation and the thermal management in related microelectronic devices. In this study, the thermal properties of n-type MePSi, prepared by electrochemical etching, have been investigated using the pulsed photothermal method. SEM observations evidence a columnar structure of pores, whose size varies between 5 and 25 nm, for the different etching depths (0.2, 1, 10, and 50 μm). Also, Fourier transform infrared (FTIR) spectroscopy has highlighted the presence of Si–H and Si–O bonds in addition to the confirmation of the porosity values and their size distribution. By means of the pulsed photothermal method (PPT), the thermal properties of MePSi such as thermal conductivity (k), volume specific heat (ρCp), and thermal contact resistance (Rth) have been determined. The thermal conductivity decreases from 8.0 to 5.0 W·m–1·K–1 as increasing the etching depth from 0.2 to 50 μm. Opposite to the monocrystalline-Si samples, the presence of Si–H and Si–O bonds in the MePSi in addition to the porosity effect is responsible for the drop of the thermal conductivity values

Photothermal Effects and Heat Conduction in Nanogranular Silicon Films

“…For example, n-type thick porous Si samples have multi-porous (nano, meso, micro) morphologies, while p+, p-type samples have single porous morphologies [ 30 ]. In general, measured = 0.19–0.53 W/mK of our Si nanogranular films are in the range of the lowest 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 ].…”

“…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, has 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 , …”

Micro-spikes formed on mesoporous silicon by UV picosecond laser irradiation

“…The results are summarized in fig. 7 The specular reflectivity spectrum of the untreated sample is typical of an electrochemicaletched layer located at the surface of the silicon wafer [35]. The amplitude and periodicity of the interferences visible in figure 7 are characteristic of a 50 µm thick layer with a porosity around 42%.…”

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]…”