Scanning tip measurement for identification of point defects
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NANO REVIEW
Open Access
Scanning tip measurement for identification of point defects László Dózsa1*, György Molnár1, Vito Raineri2, Filippo Giannazzo2, János Ferencz1, Štefan Lányi3 Abstract Self-assembled iron-silicide nanostructures were prepared by reactive deposition epitaxy of Fe onto silicon. Capacitance-voltage, current-voltage, and deep level transient spectroscopy (DLTS) were used to measure the electrical properties of Au/silicon Schottky junctions. Spreading resistance and scanning probe capacitance microscopy (SCM) were applied to measure local electrical properties. Using a preamplifier the sensitivity of DLTS was increased satisfactorily to measure transients of the scanning tip semiconductor junction. In the Fe-deposited area, Fe-related defects dominate the surface layer in about 0.5 μm depth. These defects deteriorated the Schottky junction characteristic. Outside the Fe-deposited area, Fe-related defect concentration was identified in a thin layer near the surface. The defect transients in this area were measured both in macroscopic Schottky junctions and by scanning tip DLTS and were detected by bias modulation frequency dependence in SCM. Introduction Nanostructures require investigation of local electrical characteristics with high spatial resolution [1]. Nondestructive measurement of the surface and the interfaces is critical in SOI materials [2], such techniques are technologically important in characterization of growth processes [3] and in measurement of dielectric layers [4]. Defect identification was investigated in detail using few millimeter size electrodes [5]. Metal silicide films have attracted attention because of their scientific curiosity and technical importance [6]. Fe is a critical contamination in silicon and investigation of the defects related to Fe is technologically important. In earlier studies we have investigated microscopic, structural, and electric properties of FeSi2 layers [7-10]. Noise and deep level transient spectroscopy (DLTS) investigation of bFeSi 2 quantum dots embedded in silicon show that Schottky junctions are not effective in evaluating defects in the Fe-Si system since the device current is described by space charge limited current and the depleted layer model is not applicable [11]. Scanning probe capacitance microscopy (SCM) was applied to measure the local electrical characteristics; however, the isolated quantum dots could not be resolved due to the large * Correspondence: [email protected] 1 Research Institute for Technical Physics and Materials Sciences, P.O. 49, H1525 Budapest, Hungary Full list of author information is available at the end of the article
concentration of Fe-related defects. The results show that for understanding the electrical properties of nanostructures the measurement of electric transport on nanoscale is necessary. In an earlier study we have shown that the SCM transient on the silicon surface near the Fe-contaminated region indicates surface contamination [7]. In this study we identify defects outside the Fe-deposited reg
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