Seebeck Effect in Magnetic Tunnel Junctions

Creating temperature gradients in magnetic nanostructures has resulted in a new research direction, i.e., the combination of magneto- and thermoelectric effects. Here, we demonstrate the observation of one important effect of this class: the magneto-Seebeck effect. It is observed when a magnetic configuration changes the charge based Seebeck coefficient. In particular, the Seebeck coefficient changes during the transition from a parallel to an antiparallel magnetic configuration in a tunnel junction. In that respect, it is the analog to the tunneling magnetoresistance. The Seebeck coefficients in parallel and antiparallel configuration are in the order of the voltages known from the charge-Seebeck effect. The size and sign of the effect can be controlled by the composition of the electrodes' atomic layers adjacent to the barrier and the temperature. Experimentally, we realized 8.8 % magneto-Seebeck effect, which results from a voltage change of about -8.7 {\mu}V/K from the antiparallel to the parallel direction close to the predicted value of -12.1 {\mu}V/K.Comment: 16 pages, 7 figures, 2 table

Microstructural analysis of the modifications in substrate-bound silicon-rich silicon oxide induced by continuous wave laser irradiation

Laser-irradiation of silicon-rich silicon oxides (SRSO) is a promising technique for spatially well-defined production of silicon nanocrystals (nc-Si) showing room temperature photoluminescence. In this work, we use continuous-wave (CW) laser processing to generate nc-Si in SRSO films on fused silica substrates. One main problem is damage introduced by laser processing which results in a porous layer beneath the original film surface as is consistently shown by electron tomography and energy-dispersive X-ray spectrometry. Processing conditions for damage-free nc-Si formation are identified by systematic variation of laser intensity and measuring the depth of the damaged region by transmission electron microscopy (TEM). By combining TEM imaging and analysis it is shown that the damaged region has a composition close to SiO2 which is due to a predominant loss of silicon rather than an a result of surface oxidation during laser processing

Current–voltage characteristics of manganite–titanite perovskite junctions

After a general introduction into the Shockley theory of current voltage (J–V) characteristics of inorganic and organic semiconductor junctions of different bandwidth, we apply the Shockley theory-based, one diode model to a new type of perovskite junctions with polaronic charge carriers. In particular, we studied manganite–titanate p–n heterojunctions made of n-doped SrTi1−yNbyO3, y = 0.002 and p-doped Pr1−xCaxMnO3, x = 0.34 having a strongly correlated electron system. The diffusion length of the polaron carriers was analyzed by electron beam-induced current (EBIC) in a thin cross plane lamella of the junction. In the J–V characteristics, the polaronic nature of the charge carriers is exhibited mainly by the temperature dependence of the microscopic parameters, such as the hopping mobility of the series resistance and a colossal electro-resistance (CER) effect in the parallel resistance. We conclude that a modification of the Shockley equation incorporating voltage-dependent microscopic polaron parameters is required. Specifically, the voltage dependence of the reverse saturation current density is analyzed and interpreted as a voltage-dependent electron–polaron hole–polaron pair generation and separation at the interface

Temperature and bias-voltage dependence of atomic-layer-deposited HfO2-based magnetic tunnel junctions

Fabretti S, Zierold R, Nielsch K, et al. Temperature and bias-voltage dependence of atomic-layer-deposited HfO2-based magnetic tunnel junctions. Applied Physics Letters. 2014;105(13): 132405

[Turgut Özal'a ait vefat ve başsağlığı ilanları]

Taha Toros Arşivi, Dosya No: 47-Turgut ÖzalUnutma İstanbul projesi İstanbul Kalkınma Ajansı'nın 2016 yılı "Yenilikçi ve Yaratıcı İstanbul Mali Destek Programı" kapsamında desteklenmiştir. Proje No: TR10/16/YNY/010