Limits...
Microscopic study of electrical properties of CrSi2 nanocrystals in silicon.

Dózsa L, Lányi S, Raineri V, Giannazzo F, Galkin NG - Nanoscale Res Lett (2011)

Bottom Line: Two types of samples were investigated: in one of them, the NCs were localized near the deposition depth, and in the other they migrated near the surface.The electrical interaction of the vibrating scanning tip results in virtual deformation of the surface.SCM has revealed NCs deep below the surface not seen by AFM.

View Article: PubMed Central - HTML - PubMed

Affiliation: Research Institute for Technical Physics and Materials Science, P, O, Box 49, H-1525 Budapest, Hungary. dozsa@mfa.kfki.hu.

ABSTRACT
Semiconducting CrSi2 nanocrystallites (NCs) were grown by reactive deposition epitaxy of Cr onto n-type silicon and covered with a 50-nm epitaxial silicon cap. Two types of samples were investigated: in one of them, the NCs were localized near the deposition depth, and in the other they migrated near the surface. The electrical characteristics were investigated in Schottky junctions by current-voltage and capacitance-voltage measurements. Atomic force microscopy (AFM), conductive AFM and scanning probe capacitance microscopy (SCM) were applied to reveal morphology and local electrical properties. The scanning probe methods yielded specific information, and tapping-mode AFM has shown up to 13-nm-high large-area protrusions not seen in the contact-mode AFM. The electrical interaction of the vibrating scanning tip results in virtual deformation of the surface. SCM has revealed NCs deep below the surface not seen by AFM. The electrically active probe yielded significantly better spatial resolution than AFM. The conductive AFM measurements have shown that the Cr-related point defects near the surface are responsible for the leakage of the macroscopic Schottky junctions, and also that NCs near the surface are sensitive to the mechanical and electrical stress induced by the scanning probe.

No MeSH data available.


Related in: MedlinePlus

Characteristics of the Schottky junctions on Si/CrSi2 NC/Si structures: I-V measured at room temperature (a) and at 77 K (b); C-V measured at room temperature (c) and at 77 K (d).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC3211265&req=5

Figure 1: Characteristics of the Schottky junctions on Si/CrSi2 NC/Si structures: I-V measured at room temperature (a) and at 77 K (b); C-V measured at room temperature (c) and at 77 K (d).

Mentions: Typical current-voltage (I-V) characteristics in Schottky junctions of the two different types measured at 297 K are shown in Figure 1a, and those measured at 77 K are shown in Figure 1b. The series resistance dominates the forward, and leakage resistance dominates the reverse I-V characteristics in samples where the NCs migrated near the silicon surface. The typical leakage resistance is about 1 kΩ at 297 K and increases to 56 kΩ at 77 K. The cited resistance values are not related to the figures. The figures demonstrate the different types of I-Vs. The leakage resistance is thermally activated, indicating that the Fermi level in the cap is pinned by point defects at about 160 meV from the conduction band. The thermal activation of the leakage resistance was evaluated by linear fits to the reverse I-V and by plotting the fitted resistance values as a function of reciprocal temperature. The capacitance-voltage (C-V) characteristics of the junctions measured at room temperature are shown in Figure 1c, and those measured at 77 K are shown in Figure 1d. Schottky junction capacitance 260 pF--indicated as a line in Figure 1c--corresponds to 50-nm depleted layer thickness, equal to the nominal cap thickness. Below -1 V reverse bias at low temperature, the doping calculated from the 1/C2-voltage plot is appropriate for the semiconductor substrate in both types of samples. The doping concentration profile was calculated from the C-V characteristics measured at different temperatures (not shown in the figures). The calculated doping profiles in the two type of samples are shown in Figure 2. The samples with NCs migrating near the surface show high concentration of donors, while in samples with NCs remaining near 50-nm deposition depth, the donor concentration is low.


Microscopic study of electrical properties of CrSi2 nanocrystals in silicon.

Dózsa L, Lányi S, Raineri V, Giannazzo F, Galkin NG - Nanoscale Res Lett (2011)

Characteristics of the Schottky junctions on Si/CrSi2 NC/Si structures: I-V measured at room temperature (a) and at 77 K (b); C-V measured at room temperature (c) and at 77 K (d).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3211265&req=5

Figure 1: Characteristics of the Schottky junctions on Si/CrSi2 NC/Si structures: I-V measured at room temperature (a) and at 77 K (b); C-V measured at room temperature (c) and at 77 K (d).
Mentions: Typical current-voltage (I-V) characteristics in Schottky junctions of the two different types measured at 297 K are shown in Figure 1a, and those measured at 77 K are shown in Figure 1b. The series resistance dominates the forward, and leakage resistance dominates the reverse I-V characteristics in samples where the NCs migrated near the silicon surface. The typical leakage resistance is about 1 kΩ at 297 K and increases to 56 kΩ at 77 K. The cited resistance values are not related to the figures. The figures demonstrate the different types of I-Vs. The leakage resistance is thermally activated, indicating that the Fermi level in the cap is pinned by point defects at about 160 meV from the conduction band. The thermal activation of the leakage resistance was evaluated by linear fits to the reverse I-V and by plotting the fitted resistance values as a function of reciprocal temperature. The capacitance-voltage (C-V) characteristics of the junctions measured at room temperature are shown in Figure 1c, and those measured at 77 K are shown in Figure 1d. Schottky junction capacitance 260 pF--indicated as a line in Figure 1c--corresponds to 50-nm depleted layer thickness, equal to the nominal cap thickness. Below -1 V reverse bias at low temperature, the doping calculated from the 1/C2-voltage plot is appropriate for the semiconductor substrate in both types of samples. The doping concentration profile was calculated from the C-V characteristics measured at different temperatures (not shown in the figures). The calculated doping profiles in the two type of samples are shown in Figure 2. The samples with NCs migrating near the surface show high concentration of donors, while in samples with NCs remaining near 50-nm deposition depth, the donor concentration is low.

Bottom Line: Two types of samples were investigated: in one of them, the NCs were localized near the deposition depth, and in the other they migrated near the surface.The electrical interaction of the vibrating scanning tip results in virtual deformation of the surface.SCM has revealed NCs deep below the surface not seen by AFM.

View Article: PubMed Central - HTML - PubMed

Affiliation: Research Institute for Technical Physics and Materials Science, P, O, Box 49, H-1525 Budapest, Hungary. dozsa@mfa.kfki.hu.

ABSTRACT
Semiconducting CrSi2 nanocrystallites (NCs) were grown by reactive deposition epitaxy of Cr onto n-type silicon and covered with a 50-nm epitaxial silicon cap. Two types of samples were investigated: in one of them, the NCs were localized near the deposition depth, and in the other they migrated near the surface. The electrical characteristics were investigated in Schottky junctions by current-voltage and capacitance-voltage measurements. Atomic force microscopy (AFM), conductive AFM and scanning probe capacitance microscopy (SCM) were applied to reveal morphology and local electrical properties. The scanning probe methods yielded specific information, and tapping-mode AFM has shown up to 13-nm-high large-area protrusions not seen in the contact-mode AFM. The electrical interaction of the vibrating scanning tip results in virtual deformation of the surface. SCM has revealed NCs deep below the surface not seen by AFM. The electrically active probe yielded significantly better spatial resolution than AFM. The conductive AFM measurements have shown that the Cr-related point defects near the surface are responsible for the leakage of the macroscopic Schottky junctions, and also that NCs near the surface are sensitive to the mechanical and electrical stress induced by the scanning probe.

No MeSH data available.


Related in: MedlinePlus