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

Tailored Schottky barrier width and Hanle spin signals for p-type Si.Si devices with four different boron doping concentrations were studied. (a) Energy-band diagram for p-type Si/SiO2/Co showing doping-dependent Schottky barrier width. (b) Bias voltage dependence of current density and RjuncA at 300 K. (c) Hanle spin signals measured at 300 K.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

f5: Tailored Schottky barrier width and Hanle spin signals for p-type Si.Si devices with four different boron doping concentrations were studied. (a) Energy-band diagram for p-type Si/SiO2/Co showing doping-dependent Schottky barrier width. (b) Bias voltage dependence of current density and RjuncA at 300 K. (c) Hanle spin signals measured at 300 K.

Mentions: In the previous sections, we have presented results on spin injection into degenerate Si with very narrow Schottky barriers, where the transport process is dominated by direct tunneling. However, in nondegenerate Si, the presence of a wider Schottky barrier alters the transport process. In order to determine the effects of the Schottky barrier profile on the spin injection and detection process, we perform experiments on Si with different doping densities, i.e. with different Schottky barrier widths W and hence resistances (see Fig. 5a). We use p-type Si with four different boron doping concentrations (see Table I for the parameters of the Si samples). The preparation conditions of the ozone-oxidized SiO2 tunnel barrier and ferromagnetic contacts are kept identical for all these devices. Figure 5b shows the significant decrease in current density or increase in resistance in the reverse bias regime upon lowering the boron doping density, showing the transition of the contacts from tunneling to diodic behavior. Such systematic variation of the Schottky barrier resistance is quite useful in verifying the proposed spin-transport models.


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

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

Tailored Schottky barrier width and Hanle spin signals for p-type Si.Si devices with four different boron doping concentrations were studied. (a) Energy-band diagram for p-type Si/SiO2/Co showing doping-dependent Schottky barrier width. (b) Bias voltage dependence of current density and RjuncA at 300 K. (c) Hanle spin signals measured at 300 K.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

f5: Tailored Schottky barrier width and Hanle spin signals for p-type Si.Si devices with four different boron doping concentrations were studied. (a) Energy-band diagram for p-type Si/SiO2/Co showing doping-dependent Schottky barrier width. (b) Bias voltage dependence of current density and RjuncA at 300 K. (c) Hanle spin signals measured at 300 K.
Mentions: In the previous sections, we have presented results on spin injection into degenerate Si with very narrow Schottky barriers, where the transport process is dominated by direct tunneling. However, in nondegenerate Si, the presence of a wider Schottky barrier alters the transport process. In order to determine the effects of the Schottky barrier profile on the spin injection and detection process, we perform experiments on Si with different doping densities, i.e. with different Schottky barrier widths W and hence resistances (see Fig. 5a). We use p-type Si with four different boron doping concentrations (see Table I for the parameters of the Si samples). The preparation conditions of the ozone-oxidized SiO2 tunnel barrier and ferromagnetic contacts are kept identical for all these devices. Figure 5b shows the significant decrease in current density or increase in resistance in the reverse bias regime upon lowering the boron doping density, showing the transition of the contacts from tunneling to diodic behavior. Such systematic variation of the Schottky barrier resistance is quite useful in verifying the proposed spin-transport models.

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