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Nanoscale characterization of electrical transport at metal/3C-SiC interfaces.

Eriksson J, Roccaforte F, Reshanov S, Leone S, Giannazzo F, Lonigro R, Fiorenza P, Raineri V - Nanoscale Res Lett (2011)

Bottom Line: In this case, annealing at 500°C resulted in a reduction of the leakage current and an increase of the Schottky barrier height (from 0.77 to 1.12 eV).A structural analysis of the reaction zone carried out by transmission electron microscopy [TEM] and X-ray diffraction showed that the improved electrical properties can be attributed to a consumption of the surface layer of SiC due to silicide (Pt2Si) formation.The degradation of Schottky characteristics at higher temperatures (up to 900°C) could be ascribed to the out-diffusion and aggregation of carbon into clusters, observed by TEM analysis.

View Article: PubMed Central - HTML - PubMed

Affiliation: CNR-IMM, Strada VIII n, 5, Zona Industriale, 95121, Catania, Italy. jens.eriksson@imm.cnr.it.

ABSTRACT
In this work, the transport properties of metal/3C-SiC interfaces were monitored employing a nanoscale characterization approach in combination with conventional electrical measurements. In particular, using conductive atomic force microscopy allowed demonstrating that the stacking fault is the most pervasive, electrically active extended defect at 3C-SiC(111) surfaces, and it can be electrically passivated by an ultraviolet irradiation treatment. For the Au/3C-SiC Schottky interface, a contact area dependence of the Schottky barrier height (ΦB) was found even after this passivation, indicating that there are still some electrically active defects at the interface. Improved electrical properties were observed in the case of the Pt/3C-SiC system. In this case, annealing at 500°C resulted in a reduction of the leakage current and an increase of the Schottky barrier height (from 0.77 to 1.12 eV). A structural analysis of the reaction zone carried out by transmission electron microscopy [TEM] and X-ray diffraction showed that the improved electrical properties can be attributed to a consumption of the surface layer of SiC due to silicide (Pt2Si) formation. The degradation of Schottky characteristics at higher temperatures (up to 900°C) could be ascribed to the out-diffusion and aggregation of carbon into clusters, observed by TEM analysis.

No MeSH data available.


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Passivation of localized leakage currents, passing through SFs at the as-grown 3C-SiC surface, by UV irradiation. C-AFM morphology (top) and current maps (bottom) of an as-grown 3C-SiC(111) surface at a tip bias of −2 V (a) showing localized leakage currents passing through stacking faults. The AFM morphology of the UV-irradiated 3C-SiC surface after a wet oxide etch revealed trenches in the SFs, suggesting that their passivation is due to a local oxidation at these defects. The I-V characteristics measured on Au/3C-SiC diodes with a contact radius of 20 μm exhibited greatly reduced leakage currents after passivation (c).
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Figure 1: Passivation of localized leakage currents, passing through SFs at the as-grown 3C-SiC surface, by UV irradiation. C-AFM morphology (top) and current maps (bottom) of an as-grown 3C-SiC(111) surface at a tip bias of −2 V (a) showing localized leakage currents passing through stacking faults. The AFM morphology of the UV-irradiated 3C-SiC surface after a wet oxide etch revealed trenches in the SFs, suggesting that their passivation is due to a local oxidation at these defects. The I-V characteristics measured on Au/3C-SiC diodes with a contact radius of 20 μm exhibited greatly reduced leakage currents after passivation (c).

Mentions: The micrographs in Figure 1a, obtained by applying a bias voltage of −2 V to the C-AFM tip that is scanned in contact mode on the semiconductor surface, show the morphology and the corresponding current map of the as-grown 3C-SiC(111) surface. As can be seen, leakage current preferentially flows through SFs, and several current maps determined on different areas on the sample alongside plan-view TEM analysis (not shown here, see, e.g., [9]) showed these to be the most pervasive extended defects affecting the electrical properties at the 3C-SiC surface and, hence, at the contact interface. In contrast, similar current maps measured after a UV surface treatment (as described in "Experimental") showed no localized leakage current through the SFs above the detection limit (I < 50 fA). Consequently, the electrical conduction through SFs at the 3C-SiC(111) surface can be suppressed by UV irradiation, during which ozone is generated. UV ozone treatment is known to remove surface defects in SiC related to carbon atoms due to oxidation [10], and SFs arriving at the 3C-SiC(111) have a C termination [17]. Indeed, the AFM morphology map in Figure 1b, obtained on the UV-irradiated 3C-SiC surface after selective wet oxide etching, reveals trenches of a few nanometers at the SF locations. Hence, the passivation of the SFs may result from a preferential oxidation occurring locally inside these defects where the polarity is shifted with respect to the Si-terminated (111) surface [17].


Nanoscale characterization of electrical transport at metal/3C-SiC interfaces.

Eriksson J, Roccaforte F, Reshanov S, Leone S, Giannazzo F, Lonigro R, Fiorenza P, Raineri V - Nanoscale Res Lett (2011)

Passivation of localized leakage currents, passing through SFs at the as-grown 3C-SiC surface, by UV irradiation. C-AFM morphology (top) and current maps (bottom) of an as-grown 3C-SiC(111) surface at a tip bias of −2 V (a) showing localized leakage currents passing through stacking faults. The AFM morphology of the UV-irradiated 3C-SiC surface after a wet oxide etch revealed trenches in the SFs, suggesting that their passivation is due to a local oxidation at these defects. The I-V characteristics measured on Au/3C-SiC diodes with a contact radius of 20 μm exhibited greatly reduced leakage currents after passivation (c).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3211166&req=5

Figure 1: Passivation of localized leakage currents, passing through SFs at the as-grown 3C-SiC surface, by UV irradiation. C-AFM morphology (top) and current maps (bottom) of an as-grown 3C-SiC(111) surface at a tip bias of −2 V (a) showing localized leakage currents passing through stacking faults. The AFM morphology of the UV-irradiated 3C-SiC surface after a wet oxide etch revealed trenches in the SFs, suggesting that their passivation is due to a local oxidation at these defects. The I-V characteristics measured on Au/3C-SiC diodes with a contact radius of 20 μm exhibited greatly reduced leakage currents after passivation (c).
Mentions: The micrographs in Figure 1a, obtained by applying a bias voltage of −2 V to the C-AFM tip that is scanned in contact mode on the semiconductor surface, show the morphology and the corresponding current map of the as-grown 3C-SiC(111) surface. As can be seen, leakage current preferentially flows through SFs, and several current maps determined on different areas on the sample alongside plan-view TEM analysis (not shown here, see, e.g., [9]) showed these to be the most pervasive extended defects affecting the electrical properties at the 3C-SiC surface and, hence, at the contact interface. In contrast, similar current maps measured after a UV surface treatment (as described in "Experimental") showed no localized leakage current through the SFs above the detection limit (I < 50 fA). Consequently, the electrical conduction through SFs at the 3C-SiC(111) surface can be suppressed by UV irradiation, during which ozone is generated. UV ozone treatment is known to remove surface defects in SiC related to carbon atoms due to oxidation [10], and SFs arriving at the 3C-SiC(111) have a C termination [17]. Indeed, the AFM morphology map in Figure 1b, obtained on the UV-irradiated 3C-SiC surface after selective wet oxide etching, reveals trenches of a few nanometers at the SF locations. Hence, the passivation of the SFs may result from a preferential oxidation occurring locally inside these defects where the polarity is shifted with respect to the Si-terminated (111) surface [17].

Bottom Line: In this case, annealing at 500°C resulted in a reduction of the leakage current and an increase of the Schottky barrier height (from 0.77 to 1.12 eV).A structural analysis of the reaction zone carried out by transmission electron microscopy [TEM] and X-ray diffraction showed that the improved electrical properties can be attributed to a consumption of the surface layer of SiC due to silicide (Pt2Si) formation.The degradation of Schottky characteristics at higher temperatures (up to 900°C) could be ascribed to the out-diffusion and aggregation of carbon into clusters, observed by TEM analysis.

View Article: PubMed Central - HTML - PubMed

Affiliation: CNR-IMM, Strada VIII n, 5, Zona Industriale, 95121, Catania, Italy. jens.eriksson@imm.cnr.it.

ABSTRACT
In this work, the transport properties of metal/3C-SiC interfaces were monitored employing a nanoscale characterization approach in combination with conventional electrical measurements. In particular, using conductive atomic force microscopy allowed demonstrating that the stacking fault is the most pervasive, electrically active extended defect at 3C-SiC(111) surfaces, and it can be electrically passivated by an ultraviolet irradiation treatment. For the Au/3C-SiC Schottky interface, a contact area dependence of the Schottky barrier height (ΦB) was found even after this passivation, indicating that there are still some electrically active defects at the interface. Improved electrical properties were observed in the case of the Pt/3C-SiC system. In this case, annealing at 500°C resulted in a reduction of the leakage current and an increase of the Schottky barrier height (from 0.77 to 1.12 eV). A structural analysis of the reaction zone carried out by transmission electron microscopy [TEM] and X-ray diffraction showed that the improved electrical properties can be attributed to a consumption of the surface layer of SiC due to silicide (Pt2Si) formation. The degradation of Schottky characteristics at higher temperatures (up to 900°C) could be ascribed to the out-diffusion and aggregation of carbon into clusters, observed by TEM analysis.

No MeSH data available.


Related in: MedlinePlus