Study of nano-porous silicon with low thermal conductivity as thermal insulating material

Recently discovered phenomenon of extremely low thermal conductivity of nan o-porous silicon (nano-PS) is discussed in detail. A theoretical model desc ribing specific mechanisms of heat transport in as-prepared and oxidized na no-PS layers is described. The theoretical estimations are in a good agreem ent with experimental data obtained earlier. The low thermal conductivity v alues allow to use this promising material as thermal insulator in microsen sors and microsystems. To ensure an efficient thermal isolation, a nano-PS layer has to be as thick as possible and mechanically stable. We describe h ere the procedures to form thick (up to 200 mu m) and stable nano-PS layers . Distribution of Si oxidized fraction along the layer thickness after ther mal oxidation in dry O-2 atmosphere at 300 degrees C during 1 h is studied.