Organic materials and devices into the transport properties of spin

Title: Organic materials and devices into the transport properties of spin Author: Zhang Yubin Degree-granting units: Shandong University Keywords: Organic spintronics;; polaron;; bipolarons;; spin polarization;; interface penetration of magnetic atoms Abstract: Spintronics is great research potential of modern condensed matter physics, one of the areas. Different from the traditional electronics, electric spin
Sub-study of electronic properties and charge Magnetic lifter characteristics of the spin combination, and the core is the study of spin-polarized electron injection, transport, detection and
Spin control, the aim is to device electrical characteristics, optical properties and magnetic characteristics are combined to achieve a new type of spin electronic devices. From
Spin electronics is a major development in electronics, the last decade not only led to high-density memory devices such major applications of the emergence of the
And also led to some fundamental physical revolution, such as the spin current, self-spinning, spin Hall effect and other new physical concept or phenomenon
. Spintronics devices, including magnetic semiconductors and ferromagnetic metals or insulators, superconductors, conductors, semiconductors and other complex configuration, but also
Made in recent years, including functions of solid organic small molecules or nano-devices. Currently, a number of prototype devices have been designed, such as Datta and
Das designed the first spin transistors. The practical application of the device needs to address how to effectively spin-polarized current injection semiconductor
Problem, which requires theoretical and experimental studies accurately describe spin injection, evolution and interface effects and so on. The current study found that injection of power
Flow of spin polarization and the ratio of two materials is closely related to the resistance, and resistance does not match is the http://www.999magnet.com/products/131-magnetic-lifter traditional material is difficult to achieve high spin injection efficiency
Rate of reason. Compared with ordinary solid materials, soft organic semiconductors (OSCs: Organic semiconductors) can be
Magnetic layer to form a good contact, can effectively reduce the spin scattering at the interface. As the organic material weak spin - orbit coupling and hyperfine
Interaction, carrier spin relaxation time is rather long, so the organic material is spin-polarized transport to achieve an ideal candidate material. Different
Conventional inorganic semiconductors in the carrier is electronic, organic semiconductors is carrier in the polaron, bipolaron and soliton cases such as quasi-
Son, they are more complex spin-charge relationship, so rich in organic spin devices have more features. Small molecules to polymers, it
Of organic materials such as the electromagnetic properties of light more in-depth knowledge of, or in terms of quantum theory from the classical theory, have been with the real
Experience comparable to the theoretical results. In particular, in recent years, organic semiconductor electronics and spin combination, it has been some very
Exciting new phenomena and new effects, the line branches into a new discipline - Organic Spintronics. Organic Spintronics
Is the study of organic functional materials and related devices in the spins, destroy, transfer and storage, and other physical phenomena and physical mechanisms of discipline
. It contains organic materials and chemical cross-and interdisciplinary physics of spintronics two areas. Combine the two to explore the organic
Materials in the field of application of spintronics is clearly an important value of basic research and potential application background, which is the current international
Close attention to a number of group research. 2002 Dediu first reported group of organic material in the spin injection
Into and transport, they used semi-metallic CMR materials La_xSr_ (1-x) MnO_3 (LSMO) for the polarized electron donor, the organic layer
sexithenyl (T_6), a negative magnetoresistance was found, indicating that the spin polarization in the organic layer into memory, the transport current between two electrodes is
Spin polarization. In recent years, a number of experimental verification of the organic material in the spin injection and transport phenomena. As in 2004, Xiong
, Who prepared LSMO/Alq_3/Co spin valve, the measured temperature can be achieved under 40% of the magnetoresistance: Majumdar, who used to make LSMO
Spin-polarized electrodes, studied LSMO / polymer / Co structure into the phenomenon of spin-polarized, focused on the impact of interface effect
And so on. Of organic semiconductor spin injection and transport in the theory of human research include Xie et quantum theory and in behalf of Smith and
Z. G. Yu and other man-made on behalf of both the classical theory. The former can describe the microscopic mechanism of spin-polarized transport, which can be a
These physical quantities can be compared with experiment. In recent years, it has been on the organic material in the spin-polarized injection and transport a lot of reasons
On the work. However, some specific issues that people are not very clear, for example, an organic semiconductor between the polaron and bipolaron transformation
Spin-polarized injection and transport of the impact; organic semiconductors bipolarons what factors determine the concentration? Ferromagnetic / organic semiconductor industry
Magnetic atoms on the surface of the penetration of organic semiconductor spin-polarized injection and transport for the influence. Therefore, this paper will be based on the classic
Drift - diffusion theory issues relevant to the above study, research contents and results are as follows: 1, of the polaron and bipolaron
Spin-polarized injection and transport of Since organic semiconductors with strong electron - lattice interaction, so the injected power
Sub-lattice distortion will result, eventually in some of the charge self-trapping states, such as polarons and bipolarons, etc. Polaron with the 1 / 2 spin, but
Bipolarons do not carry spin. Organic semiconductors in polarons and bipolarons is not entirely unrelated, in the external conditions such as temperature,
Pressure or external field and so on, the two spin polarons can annihilate into a non-spin bipolarons, a bipolaron can
Dissociation into two polarons. Street, who was not related to the establishment of spin-polaron interaction of the macro model to analyze the polaron and
Translation issues between the bipolarons. People do not consider between polarons and bipolarons on the basis of the transformation, since they are already
The role of spin transport in the initial understanding. However, as mentioned above, between polarons and bipolarons into existence, this transfer
Of spin-polarized injection and transport of the impact will be what? In this paper, based on the Street model of a spin-dependent polar
Annihilator - polaron interaction model to describe the polaron and bipolaron transformation between, and to study the organic semiconductor devices from
Spin injection and transport. Based contains between polaron and bipolaron transformation of spin-flip effect and the effect of polaron drift - expanded
Dispersion equation, we calculated the spin carrying polarons and spin bipolarons do not carry the evolution. Found in a polaron
Machine spin-polarized transport in semiconductors play a major role. But unlike traditional non-organic semiconductor in the case, do not carry spin
The bipolarons will affect organic spin polarization device. Finally, we discuss the carrier's spin-flip time and the mobility of organic
Devices in the spin polarization effects, we found that a large spin-flip time or mobility is conducive to spin transport in organic semiconductors
. 2, the organic spin devices Factors affecting the concentration of bipolarons In the third chapter, and by considering two-polaron
Between polaron transformation, we find that bipolarons will spin-polarized transport has important implications. In addition, Bobbert and others that produce
Health Organic magnetoresistance (OMAR: organic magnetoresistance) due through the hyperfine interaction, external magnetic field affects the self-
Spin singlet formation probability, thus affecting the bipolarons content. Thus, the bipolaron as a carrier in the organic spin devices from
Spin-related transport plays an important role, its concentration in the organic spin to some extent determine device performance. Consider polarons and bipolar
Between polaron transformation, we based on drift - diffusion equation, the bipolaron concentration distribution, discussed the spin-flip time,
Carrier mobility rate of the bipolaron concentration. The study found that the polaron spin-flip time does not affect the size of the bipolaron
Saturation concentration, but the spin-flip time of the split in the transport process is not conducive to the creation of bipolarons, which indicates a spin-degenerate states do not
Conducive to the creation of bipolarons. We also found that the size of the migration rate of the saturation concentration of bipolarons has no effect. But the bipolaron
Saturation concentration with the bipolaron and polaron mobility ratio between the decreases. 3, Co / organic semiconductor structures
Co penetration of spin-polarized transport of In organic devices such as "Co / organic semiconductor / LSMO" the preparation process, Co atoms
Will penetrate into the organic layer to form a soft magnetic permeability layer. We consider the organic layer contains two sub-layers: a magnetic permeability layer and pure
Machine layer, and the establishment of macro-dynamics of spin-dependent drift - diffusion equations of the magnetic permeability layer to the spin polarization and magnetoresistance device
Impact. We found that the magnetic permeability layer is different from the pure spin-flip time of the organic layer and the migration rate, it will change the spin of the input
Transport. As the penetration level of impurity atoms or clusters of magnetization, the reversal time will be different in different spin, spin-flip time of this split
Split will be beneficial spin-polarization of the transport. Since the additional scattered Co atoms, the magnetic polaron penetration layer is less than the net migration rate
Net organic layer, which will weaken the organic layer spin polarization is not conducive to spin-polarized transport. For a given device, we discuss
The thickness of the magnetic penetration rate of spin polarization effects. We also calculated using Julliere a "Co / organic semiconductor / LSMO" device
Pieces of magnetic resistance, and the experimental data obtained good results. Finally, we discuss the interface magnetic penetration into the impact of the spin
Ring, found under the influence of the magnetic permeability, the interface is spin selective, the greater the penetration layer magnetization, spin selectivity is stronger, the more
Conducive to spin injection. Degree Year: 2009