Limits...
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

Bias dependence of spin signal with tailored Schottky barrier width at room temperature.(a) Bias dependence of Hanle spin signals for four different boron doping concentrations in p-type Si. The degenerate p++ Si device shows normal Hanle signal behavior, whereas the nondegenerate devices (p+, p and p- Si) show anomalous sign reversal. The inset shows the low bias regime, in order to emphasize the sign reversal of the spin signals. (b) Hanle curves at 100 mV (left panel) and 500 mV (right panel) demonstrating the sign reversal exists only in the low bias regime. A control sample with nonmagnetic layer between FM and tunnel barrier demonstrates clearly the origin of the spin signal in the Si band. (c) RSA with bias voltage for four devices with different boron doping concentrations in Si. (d) Energy-band diagram showing different possible spin-transport mechanisms across the tunnel junction, depending on the resistance of the tunnel and Schottky barrier. For a fixed SiO2 tunnel-barrier resistance, a low Schottky barrier resistance leads primarily to direct tunneling between the ferromagnet and the Si (1). With increasing Schottky barrier resistance, the two-step tunneling into Si via localized states (2), and the tunneling between the ferromagnet and the localized states at the interface (3), become more dominant.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC3824168&req=5

f6: Bias dependence of spin signal with tailored Schottky barrier width at room temperature.(a) Bias dependence of Hanle spin signals for four different boron doping concentrations in p-type Si. The degenerate p++ Si device shows normal Hanle signal behavior, whereas the nondegenerate devices (p+, p and p- Si) show anomalous sign reversal. The inset shows the low bias regime, in order to emphasize the sign reversal of the spin signals. (b) Hanle curves at 100 mV (left panel) and 500 mV (right panel) demonstrating the sign reversal exists only in the low bias regime. A control sample with nonmagnetic layer between FM and tunnel barrier demonstrates clearly the origin of the spin signal in the Si band. (c) RSA with bias voltage for four devices with different boron doping concentrations in Si. (d) Energy-band diagram showing different possible spin-transport mechanisms across the tunnel junction, depending on the resistance of the tunnel and Schottky barrier. For a fixed SiO2 tunnel-barrier resistance, a low Schottky barrier resistance leads primarily to direct tunneling between the ferromagnet and the Si (1). With increasing Schottky barrier resistance, the two-step tunneling into Si via localized states (2), and the tunneling between the ferromagnet and the localized states at the interface (3), become more dominant.

Mentions: Studying the bias dependence of the Hanle spin signals is an excellent way to investigate the role of the Schottky barrier, as the applied bias voltage defines the energy profile at which both spin injection and detection take place. Figure 6a shows this bias dependence of the Hanle signals on the different boron doped Si devices. With decreasing doping concentration, the width of the Schottky barrier increased, leading to increased resistance, which in turn yielded an unusual sign change in the Hanle signal at low bias voltages.


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

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

Bias dependence of spin signal with tailored Schottky barrier width at room temperature.(a) Bias dependence of Hanle spin signals for four different boron doping concentrations in p-type Si. The degenerate p++ Si device shows normal Hanle signal behavior, whereas the nondegenerate devices (p+, p and p- Si) show anomalous sign reversal. The inset shows the low bias regime, in order to emphasize the sign reversal of the spin signals. (b) Hanle curves at 100 mV (left panel) and 500 mV (right panel) demonstrating the sign reversal exists only in the low bias regime. A control sample with nonmagnetic layer between FM and tunnel barrier demonstrates clearly the origin of the spin signal in the Si band. (c) RSA with bias voltage for four devices with different boron doping concentrations in Si. (d) Energy-band diagram showing different possible spin-transport mechanisms across the tunnel junction, depending on the resistance of the tunnel and Schottky barrier. For a fixed SiO2 tunnel-barrier resistance, a low Schottky barrier resistance leads primarily to direct tunneling between the ferromagnet and the Si (1). With increasing Schottky barrier resistance, the two-step tunneling into Si via localized states (2), and the tunneling between the ferromagnet and the localized states at the interface (3), become more dominant.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

f6: Bias dependence of spin signal with tailored Schottky barrier width at room temperature.(a) Bias dependence of Hanle spin signals for four different boron doping concentrations in p-type Si. The degenerate p++ Si device shows normal Hanle signal behavior, whereas the nondegenerate devices (p+, p and p- Si) show anomalous sign reversal. The inset shows the low bias regime, in order to emphasize the sign reversal of the spin signals. (b) Hanle curves at 100 mV (left panel) and 500 mV (right panel) demonstrating the sign reversal exists only in the low bias regime. A control sample with nonmagnetic layer between FM and tunnel barrier demonstrates clearly the origin of the spin signal in the Si band. (c) RSA with bias voltage for four devices with different boron doping concentrations in Si. (d) Energy-band diagram showing different possible spin-transport mechanisms across the tunnel junction, depending on the resistance of the tunnel and Schottky barrier. For a fixed SiO2 tunnel-barrier resistance, a low Schottky barrier resistance leads primarily to direct tunneling between the ferromagnet and the Si (1). With increasing Schottky barrier resistance, the two-step tunneling into Si via localized states (2), and the tunneling between the ferromagnet and the localized states at the interface (3), become more dominant.
Mentions: Studying the bias dependence of the Hanle spin signals is an excellent way to investigate the role of the Schottky barrier, as the applied bias voltage defines the energy profile at which both spin injection and detection take place. Figure 6a shows this bias dependence of the Hanle signals on the different boron doped Si devices. With decreasing doping concentration, the width of the Schottky barrier increased, leading to increased resistance, which in turn yielded an unusual sign change in the Hanle signal at low bias voltages.

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