Current transport and thermoelectric properties of very high power factor Fe₃O₄/SiO₂/p-type Si(001) devices

Abstract

The current transport and thermoelectric properties of Fe 3 O 4 / SiO 2 / p-type Si (001) heterostructures with Fe 3 O 4 thicknesses of 150, 200, and 350 nm have been investigated between 100 and 300 K. We observe a sharp drop of the in-plane resistivity at 200K due to the onset of conduction along the Si / SiO 2 interface related to tunneling of electrons from the Fe 3 O 4 into the accumulation layer of holes at the Si / SiO 2 interface, whose existence was confirmed by capacitance-voltage measurements and a two band analysis of the Hall effect. This is accompanied by a large increase of the Seebeck coefficient reaching +1000 μV/K at 300K that is related to holes in the p-type Si(001) and gives a power factor of 70 mW/K 2 m when the Fe 3 O 4 layer thickness is reduced down to 150 nm. We show that most of the current flows in the Fe 3 O 4 layer at 300 K, while the Fe 3 O 4 / SiO 2 / p-type Si(001) heterostructures behave like tunneling p-n junctions in the transverse direction.

Negative differential resistance and magnetotransport in Fe3O4/SiO2/Si heterostructures

“…Figure 2(a) shows the I-V curves of the Fe 3 O 4 /SiO 2 /n-Si heterostructure. In the current range of 60.1 mA, the I-V curves are almost linear and symmetric above 200 K, while nonlinear and asymmetric below 200 K. In the current range of 610 mA, the I-V curves exhibit a backward diode-like rectifying behavior, 27,28 as shown in the inset of Fig. 2(a).…”

“…The I-V correlations can be described as . 27,28 As temperature decreases below 100 K, the I-V curves exhibit NDR, i.e., the differential resistance DV/DI < 0. By using the current source, the NDR shows an "S" shape, which is different from the "N" shape NDR with a voltage source.…”

“…In previous results, the NDR has never been found in Fe 3 O 4 /SiO 2 /Si heterostructures in a longitudinal two-probe manner. 27,28,37 So the NDR may derive from the inplane transport in the heterostructure. As temperature decreases, the Verwey transition increases the resistivity of In order to demonstrate the speculation of CCS, the spindependent transport in the heterostructures is investigated.…”

“…At a reverse current, the band bending at the interface results in a backward diode behavior like Fe 3 O 4 /SiO 2 /n-Si heterostructure [Fig. 3(d)] 27,28. As temperature decreases below 100 K, the I-V curves exhibit NDR, i.e., the…”

Effects of magnetism and size of nano-oxide inclusions on the thermoelectric properties of Ge0.96Bi0.06Te

“…According to our previous research studies, 28,29 Bi-doped and Ge self-doped Ge 0.96 Bi 0.06 Te shows excellent TE performance and thus is used as the matrix of GeTe-based composites in this work. We selected commercialized diamagnetic TiO 2 (work function φ = 5.1 eV 30 ) and magnetic Fe 3 O 4 ( φ = 5.5 eV 31 ) NPs as inclusions because they have larger φ than the matrix ( φ = 4.6 eV 29 ), which may build barriers for hole carriers to reduce the relatively high n H (∼3.5 × 10 20 cm −3 ) to the optimal level (1–2 × 10 20 cm −3 ). 32 The bulk TE composites were prepared by ultrasonic dispersion and rapid spark plasma sintering.…”