Theoretical Physics Group

Neutron scattering in porous silicon

On the surface of single crystal silicon wafers, porous layers can be formed by electrochemical etching and their structural properties are determined by the doping type and concentration of the substrate. In p+-type doped, (100) oriented wafers the porous structure consists of "tube-like" voids and "column-like" remains of the silicon matrix, all perpendicular with respect to the wafer surface. In small angle neutron scattering experiments the micrometer long and nanometer diameter elongated scattering elements, i.e. tubes and columns can be well represented and approximated by cylindrical form factors. The diameter and scattering length distribution of the cylindrical scattering elements were measured in a p+-type (100) oriented porous silicon wafer [1] and the tube diameters were seen to vary in the range from about 10 to 24 nm.

The small angle neutron scattering study of porous silicon layers is continuing. The pore diameter distribution data calculated from the neutron scattering intensity curves are collected and compared in various samples of (100) oriented p+-doped wafers prepared with different doping level, different porosity and different layer depth.

The structural results and data obtained by small angle neutron scattering experiments may help in understanding the practically useful chemical, electronic and other properties of porous silicon.

Relevant paper was published in

1. G. Kádár, G. Káli, Cs. Dücsö, É. Vázsonyi:
   Small-angle neutron scattering in porous silicon
   Physica B 234-236 (1997) 1014.
2. G. Kádár, É. Vázsonyi, S. Borbély, G. Káli:
   Small Angle Neutron Scattering in P+-doped Porous Silicon
   J. Porous Materials 7 (2000) 331.
3. É. Vázsonyi, G. Battistig, Z.E. Horváth, M. Fried, G. Kádár, et al.,:
   Pore propagation directions in P+ Porous Silicon
   J. Porous Materials 7 (2000) 331.