Study of Nano-Porous Silicon with Low Thermal Conductivity as Thermal Insulating Material (original) (raw)
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Nanoscale nature and low thermal conductivity of porous silicon layers
Applied Surface Science
Recently discovered phenomenon of low thermal conductivity of porous silicon (PS) layers is discussed in detail. A proposed theoretical model explains the considerable decrease of the thermal conductivity of nanoscale PS in comparison with meso-PS and bulk silicon. The thermal conductance dependence of Si/porous Si structures on the formation conditions of PS layers has been studied. By varying the values of anodisation current density and anodisation time it is possible to optimize the thermal conductance values of the Si/porous Si structures. In this way, an efficient thermal isolation can be obtained by forming thick PS layers.
Microelectronics Journal, 1999
Recently measured low thermal conductivity of as-prepared and slightly oxidized meso-porous silicon (meso-PS) offers new possibility to apply this promising material for thermal isolation in microsensors and microsystems. We report here a theoretical model describing specific mechanisms of heat transport in as-prepared and oxidized meso-PS. The model is in good agreement with experimental data obtained earlier.
Thermal isolation in microsystems with porous silicon
Sensors and Actuators A: Physical, 2002
Well-known for its promising luminescence properties, porous Si (PS) appeared also during last 5 years as a new thermal insulating material. Indeed, its extremely low thermal conductivity (TC) values (0.1±2 W m À1 K À1 ) allow to use PS for ef®cient thermal isolation in microdevices and microsystems as new alternative to usually used micromachined Si structures such as thin membranes or cantilever beams. In this paper, the state of art upon the study of thermal properties of PS is reviewed. In particular, TC measurement methods, the nature of such low TC values as well as in¯uence of the PS nanoscale morphology on its TC are discussed. Numerous technological aspects to form thick and mechanically stable PS layers are described. Finally, some thermal microdevices using PS-based thermal isolation and realized in different research laboratories over the world are presented. #
Thick oxidised porous silicon layers for the design of a biomedical thermal conductivity microsensor
Sensors and Actuators A Physical
Porous silicon (PS) offers new possibilities to be applied as thermal insulating material for microsensor design due to its low thermal conductivity (TC) value compared with TC of SiO2. A biomedical TC microsensor based on differential thermoelectric measurements has been designed using a PS substrate. In order to ensure an efficient thermal isolation in the microsensor, main thermal and geometrical characteristics of the PS layers as well as of the whole microsensor have been numerically simulated. PS layers with low TC have to be thick and mechanically stable under further processing. To form thick (50–200 μm) and stable PS layers, a new approach based on progressive changing of anodisation current density (from 100 to 25 mA/cm2) during PS formation has been elaborated. To find a suitable compromise between low TC and mechanical stability of thick PS layers, an adapted thermal oxidation recipe at moderate temperatures (500–600°C) in dry oxygen atmosphere has been applied. It leads...
Thermal Isolation with Porous Silicon
Handbook of Porous Silicon, 2014
ABSTRACT The exceptionally low thermal conductivity of highly porous silicon has led to its use as a thermal insulator within microsystems. A comprehensive review of thermal conductivity literature is provided, together with examples of its use in microsensing and microphotonic systems.
Thermal conductivity across nanostructured porous silicon films
Journal of Physics: Conference Series, 2007
This paper models the effect of pore size, pore arrangement and porosity on room temperature thermal conductivity across low porosity meso-porous silicon (meso-PS) films known as n+ and p+ type PS. Whereas the meso-PS films are simulated using a threedimensional (3D) pore network generator, the heat conduction is modeled using the Monte Carlo method (MCM) recently developed for simulating steady-state phonon transport in submicron structures. The simulations show that (i) the thermal conductivity across mesoporous films decreases when the pore size decreases or the porosity increases, in accordance with past studies. (ii) The thermal conductivity of n+ type pore network is always greater than that of p+ type due to the difference in pore morphology. Finally, the simulations corresponding to p+ type pore network are shown in good agreement with existing experimental data for low porosity p+ type PS. Such comparison confirms the validity of the current 3D modeling.
A Phenomenological Study of Pore-Size Dependent Thermal Conductivity of Porous Silicon
Acta Applicandae Mathematicae, 2012
A phonon-hydrodynamics approach is used to analyze the influence of porosity and of pore size on the reduction of the thermal conductivity in porous silicon. Different geometrical arrangements of the pores have been considered. For any given value of the porosity, the theoretical results show that for increasing Knudsen number (i.e., decreasing pore size) the effective thermal conductivity decreases whatever the geometrical arrangement of the pores is.
Thermal conductivity measurement of porous silicon by the pulsed-photothermal method
Journal of Physics D: Applied Physics, 2011
Thermal properties of two types of porous silicon are studied using the pulsed-photothermal method (PPT). This method is based on a pulsed-laser source in the nanosecond regime. A 1D analytical model is coupled with the PPT technique in order to determine thermal properties of the studied samples (thermal conductivity and volumetric heat capacity).
2014 11th International Workshop on Low Temperature Electronics (WOLTE), 2014
The thermal conductivity of highly porous Si was determined in the temperature range 5-350K. It was found that its temperature dependence is monotonic in the range 20-350K, while below 20K it shows a plateau-like behavior similar to that observed in amorphous materials. The low values of the thermal conductivity of the material in the whole temperature range studied, extended also to cryogenic temperatures, make porous Si an excellent local substrate for providing efficient thermal isolation on the Si wafer for the on-chip integration of heating and cooling devices.