Limits...
Electrical spin injection and detection in molybdenum disulfide multilayer channel

View Article: PubMed Central - PubMed

ABSTRACT

Molybdenum disulfide has recently emerged as a promising two-dimensional semiconducting material for nano-electronic, opto-electronic and spintronic applications. However, the demonstration of an electron spin transport through a semiconducting MoS2 channel remains challenging. Here we show the evidence of the electrical spin injection and detection in the conduction band of a multilayer MoS2 semiconducting channel using a two-terminal spin-valve configuration geometry. A magnetoresistance around 1% has been observed through a 450 nm long, 6 monolayer thick MoS2 channel with a Co/MgO tunnelling spin injector and detector. It is found that keeping a good balance between the interface resistance and channel resistance is mandatory for the observation of the two-terminal magnetoresistance. Moreover, the electron spin-relaxation is found to be greatly suppressed in the multilayer MoS2 channel with an in-plane spin polarization. The long spin diffusion length (approximately ∼235 nm) could open a new avenue for spintronic applications using multilayer transition metal dichalcogenides.

No MeSH data available.


Evidence of hopping transport in the contact region.(a) Arrhenius plot of the temperature dependent conductance (symbols) at different Vds from Fig. 4d and the fitting results by different hopping models (grey and pink lines). Two hopping regimes are clearly separated by T* (vertical line). (b) Band diagram of the Schottky contact region of the MoS2 device. The device can be divided into three regions. The direct tunnelling region consists of the MgO tunnelling barrier (RMgO) and one part of Schottky contact (RSC1) taken as a whole. The second region is in the tail part of depletion layer where electrons transport in a hopping behaviour (RSC2). The third region is the region where electrons either transport in the MoS2 channel by a hopping behaviour or transport in the MoS2 conduction band (RMS), depending on the carrier density.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC5385572&req=5

f6: Evidence of hopping transport in the contact region.(a) Arrhenius plot of the temperature dependent conductance (symbols) at different Vds from Fig. 4d and the fitting results by different hopping models (grey and pink lines). Two hopping regimes are clearly separated by T* (vertical line). (b) Band diagram of the Schottky contact region of the MoS2 device. The device can be divided into three regions. The direct tunnelling region consists of the MgO tunnelling barrier (RMgO) and one part of Schottky contact (RSC1) taken as a whole. The second region is in the tail part of depletion layer where electrons transport in a hopping behaviour (RSC2). The third region is the region where electrons either transport in the MoS2 channel by a hopping behaviour or transport in the MoS2 conduction band (RMS), depending on the carrier density.

Mentions: As mentioned above, an optimized MR occurs at the balance condition of a tunnel contact resistance approaching the channel spin-resistance. It seems however impossible to perfectly fulfil such condition in our device at low Vds bias. As shown in Fig. 5a, in the best MR situation, the MoS2 channel resistance (RMS) is estimated to be about 150 kΩ. The contact resistance in the investigated range of bias and temperature lies in the MΩ range, well beyond the characteristic threshold, and should then exclude any MR. How may one then reconcile with the standard spin-injection model? To clarify that point, let us focus on the T-dependence of the conductance as a fingerprint of the electronic hopping process involved in the transport. Figure 6a displays the Arrhenius plot of the T-dependence conductance at different Vds. It becomes obvious that the charge transport may be described by two distinct mechanisms in the respective high and low temperature regimes, with a characteristic threshold at T*∼70 K. For T>T*, the transport is dominated by the nearest-neighbour hopping (NNH) with a conductivity varying like G∼exp(−T0/T). For T<T*, the conductance can be fitted by a 2D variable-range hopping (VRH) equation according to G∼exp[−(T1/T)0.33]. Such characteristic T-dependence has been observed in many low-dimensional systems and is a signature of hopping transport via localized states293536. In MoS2 system, it is reported that the sulphur vacancies can introduce localized donor states inside the bandgap29. The two temperature regions for the different hopping regimes are even more pronounced at small /Vds/ (0.04 V) when the contact resistance dominates the total resistance. This highlights a transport dominated by hopping in the contact region more than in the MoS2 channel by itself.


Electrical spin injection and detection in molybdenum disulfide multilayer channel
Evidence of hopping transport in the contact region.(a) Arrhenius plot of the temperature dependent conductance (symbols) at different Vds from Fig. 4d and the fitting results by different hopping models (grey and pink lines). Two hopping regimes are clearly separated by T* (vertical line). (b) Band diagram of the Schottky contact region of the MoS2 device. The device can be divided into three regions. The direct tunnelling region consists of the MgO tunnelling barrier (RMgO) and one part of Schottky contact (RSC1) taken as a whole. The second region is in the tail part of depletion layer where electrons transport in a hopping behaviour (RSC2). The third region is the region where electrons either transport in the MoS2 channel by a hopping behaviour or transport in the MoS2 conduction band (RMS), depending on the carrier density.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5385572&req=5

f6: Evidence of hopping transport in the contact region.(a) Arrhenius plot of the temperature dependent conductance (symbols) at different Vds from Fig. 4d and the fitting results by different hopping models (grey and pink lines). Two hopping regimes are clearly separated by T* (vertical line). (b) Band diagram of the Schottky contact region of the MoS2 device. The device can be divided into three regions. The direct tunnelling region consists of the MgO tunnelling barrier (RMgO) and one part of Schottky contact (RSC1) taken as a whole. The second region is in the tail part of depletion layer where electrons transport in a hopping behaviour (RSC2). The third region is the region where electrons either transport in the MoS2 channel by a hopping behaviour or transport in the MoS2 conduction band (RMS), depending on the carrier density.
Mentions: As mentioned above, an optimized MR occurs at the balance condition of a tunnel contact resistance approaching the channel spin-resistance. It seems however impossible to perfectly fulfil such condition in our device at low Vds bias. As shown in Fig. 5a, in the best MR situation, the MoS2 channel resistance (RMS) is estimated to be about 150 kΩ. The contact resistance in the investigated range of bias and temperature lies in the MΩ range, well beyond the characteristic threshold, and should then exclude any MR. How may one then reconcile with the standard spin-injection model? To clarify that point, let us focus on the T-dependence of the conductance as a fingerprint of the electronic hopping process involved in the transport. Figure 6a displays the Arrhenius plot of the T-dependence conductance at different Vds. It becomes obvious that the charge transport may be described by two distinct mechanisms in the respective high and low temperature regimes, with a characteristic threshold at T*∼70 K. For T>T*, the transport is dominated by the nearest-neighbour hopping (NNH) with a conductivity varying like G∼exp(−T0/T). For T<T*, the conductance can be fitted by a 2D variable-range hopping (VRH) equation according to G∼exp[−(T1/T)0.33]. Such characteristic T-dependence has been observed in many low-dimensional systems and is a signature of hopping transport via localized states293536. In MoS2 system, it is reported that the sulphur vacancies can introduce localized donor states inside the bandgap29. The two temperature regions for the different hopping regimes are even more pronounced at small /Vds/ (0.04 V) when the contact resistance dominates the total resistance. This highlights a transport dominated by hopping in the contact region more than in the MoS2 channel by itself.

View Article: PubMed Central - PubMed

ABSTRACT

Molybdenum disulfide has recently emerged as a promising two-dimensional semiconducting material for nano-electronic, opto-electronic and spintronic applications. However, the demonstration of an electron spin transport through a semiconducting MoS2 channel remains challenging. Here we show the evidence of the electrical spin injection and detection in the conduction band of a multilayer MoS2 semiconducting channel using a two-terminal spin-valve configuration geometry. A magnetoresistance around 1% has been observed through a 450&thinsp;nm long, 6 monolayer thick MoS2 channel with a Co/MgO tunnelling spin injector and detector. It is found that keeping a good balance between the interface resistance and channel resistance is mandatory for the observation of the two-terminal magnetoresistance. Moreover, the electron spin-relaxation is found to be greatly suppressed in the multilayer MoS2 channel with an in-plane spin polarization. The long spin diffusion length (approximately &sim;235&thinsp;nm) could open a new avenue for spintronic applications using multilayer transition metal dichalcogenides.

No MeSH data available.