Structural and physical properties of thin copper films deposited on porous silicon

Thin transparent Cu films in the thickness range 10–40 nm are deposited by r.f.-magnetron sputtering on porous silicon (PS) anodized on p-type silicon in dark. Microstructural features of the Cu films are investigated with scanning electron microscopy (SEM), atomic force microscopy (AFM) and X-ray diffraction (XRD) techniques. The root mean square (RMS) roughness of the Cu films is found to be around 1.47 nm and the grain growth is columnar with a (1 1 1) preferred orientation and follows the Volmer–Weber mode. The photoluminescence (PL) studies showed that a broad luminescence peak of PS near the blue–green region gets blue-shifted (∼0.05 eV) with a small reduction in intensity and therefore, Cu-related PL quenching is absent. The FTIR absorption spectra on the PS/Cu structure revealed no major change of the native PS peaks but only a reduction in the relative intensity. The I–V characteristic curves further establish the Schottky nature of the diode with an ideality factor of 2.77 and a barrier height of 0.678 eV. An electroluminescence (EL) signal of small intensity could be detected for the above diode.