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Efficient spin injection into silicon and the role of the Schottky barrier.

Dankert A, Dulal RS, Dash SP - Sci Rep (2013)

Bottom Line: Implementing spin functionalities in Si, and understanding the fundamental processes of spin injection and detection, are the main challenges in spintronics.This dramatic change in the spin injection and detection processes with increased Schottky barrier resistance may be due to a decoupling of the spins in the interface states from the bulk band of Si, yielding a transition from a direct to a localized state assisted tunneling.Our study provides a deeper insight into the spin transport phenomenon, which should be considered for electrical spin injection into any semiconductor.

View Article: PubMed Central - PubMed

Affiliation: Department of Microtechnology and Nanoscience, Chalmers University of Technology, SE-41296, Göteborg, Sweden.

ABSTRACT
Implementing spin functionalities in Si, and understanding the fundamental processes of spin injection and detection, are the main challenges in spintronics. Here we demonstrate large spin polarizations at room temperature, 34% in n-type and 10% in p-type degenerate Si bands, using a narrow Schottky and a SiO2 tunnel barrier in a direct tunneling regime. Furthermore, by increasing the width of the Schottky barrier in non-degenerate p-type Si, we observed a systematic sign reversal of the Hanle signal in the low bias regime. This dramatic change in the spin injection and detection processes with increased Schottky barrier resistance may be due to a decoupling of the spins in the interface states from the bulk band of Si, yielding a transition from a direct to a localized state assisted tunneling. Our study provides a deeper insight into the spin transport phenomenon, which should be considered for electrical spin injection into any semiconductor.

No MeSH data available.


Related in: MedlinePlus

Large spin signal in degenerate n-type Si.(a) Three-terminal device geometry for injection and detection of spin polarization in Si with SiO2/Co tunnel contacts. (b) Current density versus bias voltage of the n++ Si/SiO2/Co tunnel contact measured in a three-terminal geometry at different temperatures. Insets: Temperature dependence of junction resistance at bias voltages of zero and +200 mV. (c) Energy-band diagram showing the injection of spin-polarized current through a ferromagnetic tunnel contact into n-type Si, creating a majority spin accumulation and spin-splitting of electrochemical potential in the conduction band. (d) Electrical detection of large spin polarization in n-type Si at 300 K through the Hanle effect. The spin signal of 3 mV is observed for +1 V bias voltage and +34 mA bias current. The solid line is a Lorentzian fit with a lower limit for the spin lifetime τeff = 50 ps. Left panel: The maximum spin accumulation in the absence of external magnetic field B. Right panel: A finite perpendicular magnetic field causes spin precession at the Larmor frequency, and results in the suppression of the spin accumulation.
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f1: Large spin signal in degenerate n-type Si.(a) Three-terminal device geometry for injection and detection of spin polarization in Si with SiO2/Co tunnel contacts. (b) Current density versus bias voltage of the n++ Si/SiO2/Co tunnel contact measured in a three-terminal geometry at different temperatures. Insets: Temperature dependence of junction resistance at bias voltages of zero and +200 mV. (c) Energy-band diagram showing the injection of spin-polarized current through a ferromagnetic tunnel contact into n-type Si, creating a majority spin accumulation and spin-splitting of electrochemical potential in the conduction band. (d) Electrical detection of large spin polarization in n-type Si at 300 K through the Hanle effect. The spin signal of 3 mV is observed for +1 V bias voltage and +34 mA bias current. The solid line is a Lorentzian fit with a lower limit for the spin lifetime τeff = 50 ps. Left panel: The maximum spin accumulation in the absence of external magnetic field B. Right panel: A finite perpendicular magnetic field causes spin precession at the Larmor frequency, and results in the suppression of the spin accumulation.

Mentions: To demonstrate large spin accumulations by direct tunneling, we used SiO2/Co tunnel contacts on degenerate n-type Si (n++ Si; measured electron density n = 3 · 1019 cm−3 at 300 K). The SiO2 barrier was prepared by ozone oxidation (see Methods). Electrical measurements were performed in a three-terminal geometry (Fig. 1a), in which the same tunnel interface is used for injection and for detection of spin accumulation in Si72227.


Efficient spin injection into silicon and the role of the Schottky barrier.

Dankert A, Dulal RS, Dash SP - Sci Rep (2013)

Large spin signal in degenerate n-type Si.(a) Three-terminal device geometry for injection and detection of spin polarization in Si with SiO2/Co tunnel contacts. (b) Current density versus bias voltage of the n++ Si/SiO2/Co tunnel contact measured in a three-terminal geometry at different temperatures. Insets: Temperature dependence of junction resistance at bias voltages of zero and +200 mV. (c) Energy-band diagram showing the injection of spin-polarized current through a ferromagnetic tunnel contact into n-type Si, creating a majority spin accumulation and spin-splitting of electrochemical potential in the conduction band. (d) Electrical detection of large spin polarization in n-type Si at 300 K through the Hanle effect. The spin signal of 3 mV is observed for +1 V bias voltage and +34 mA bias current. The solid line is a Lorentzian fit with a lower limit for the spin lifetime τeff = 50 ps. Left panel: The maximum spin accumulation in the absence of external magnetic field B. Right panel: A finite perpendicular magnetic field causes spin precession at the Larmor frequency, and results in the suppression of the spin accumulation.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3824168&req=5

f1: Large spin signal in degenerate n-type Si.(a) Three-terminal device geometry for injection and detection of spin polarization in Si with SiO2/Co tunnel contacts. (b) Current density versus bias voltage of the n++ Si/SiO2/Co tunnel contact measured in a three-terminal geometry at different temperatures. Insets: Temperature dependence of junction resistance at bias voltages of zero and +200 mV. (c) Energy-band diagram showing the injection of spin-polarized current through a ferromagnetic tunnel contact into n-type Si, creating a majority spin accumulation and spin-splitting of electrochemical potential in the conduction band. (d) Electrical detection of large spin polarization in n-type Si at 300 K through the Hanle effect. The spin signal of 3 mV is observed for +1 V bias voltage and +34 mA bias current. The solid line is a Lorentzian fit with a lower limit for the spin lifetime τeff = 50 ps. Left panel: The maximum spin accumulation in the absence of external magnetic field B. Right panel: A finite perpendicular magnetic field causes spin precession at the Larmor frequency, and results in the suppression of the spin accumulation.
Mentions: To demonstrate large spin accumulations by direct tunneling, we used SiO2/Co tunnel contacts on degenerate n-type Si (n++ Si; measured electron density n = 3 · 1019 cm−3 at 300 K). The SiO2 barrier was prepared by ozone oxidation (see Methods). Electrical measurements were performed in a three-terminal geometry (Fig. 1a), in which the same tunnel interface is used for injection and for detection of spin accumulation in Si72227.

Bottom Line: Implementing spin functionalities in Si, and understanding the fundamental processes of spin injection and detection, are the main challenges in spintronics.This dramatic change in the spin injection and detection processes with increased Schottky barrier resistance may be due to a decoupling of the spins in the interface states from the bulk band of Si, yielding a transition from a direct to a localized state assisted tunneling.Our study provides a deeper insight into the spin transport phenomenon, which should be considered for electrical spin injection into any semiconductor.

View Article: PubMed Central - PubMed

Affiliation: Department of Microtechnology and Nanoscience, Chalmers University of Technology, SE-41296, Göteborg, Sweden.

ABSTRACT
Implementing spin functionalities in Si, and understanding the fundamental processes of spin injection and detection, are the main challenges in spintronics. Here we demonstrate large spin polarizations at room temperature, 34% in n-type and 10% in p-type degenerate Si bands, using a narrow Schottky and a SiO2 tunnel barrier in a direct tunneling regime. Furthermore, by increasing the width of the Schottky barrier in non-degenerate p-type Si, we observed a systematic sign reversal of the Hanle signal in the low bias regime. This dramatic change in the spin injection and detection processes with increased Schottky barrier resistance may be due to a decoupling of the spins in the interface states from the bulk band of Si, yielding a transition from a direct to a localized state assisted tunneling. Our study provides a deeper insight into the spin transport phenomenon, which should be considered for electrical spin injection into any semiconductor.

No MeSH data available.


Related in: MedlinePlus