Ge-based and ZnO-based magnetic semiconductors, magnetic and transport studies

Title: Ge-based and ZnO-based magnetic semiconductors, magnetic and transport studies Author: Jiang Xia Tang Degree-granting units: Shandong University Keywords: Spintronics;; magnetic semiconductor;; Ge_ (1-x) Mn_x;; Zn_ (1-x) Co_xO;; Zn_ (1-x) Fe_xO Abstract: Spintronics is today's condensed matter physics, information science and new materials and many other areas of research focus of common concern, which the main
To study with the electron charge Neodymium Magnets and spin closely related processes, including the generation of the source spin, spin injection, spin transport, spin detection
And spin control, with the ultimate goal is to achieve a new type of spin electronic devices. Because of its guidance of a new mode of information processing and storage, large
Great ability to enhance information processing has a very broad application prospects. For the realization of spin electronic devices, you first need to generate in the material
Spin-polarized current. Generate spin-polarized current program there are many, the use of magnetic semiconductor spin-polarized current is injected into one of the main
To one of the options, so much attention magnetic semiconductors, as the field of spintronics research focus. Magnetic semiconductor is usually
Is through the of Ⅲ - Ⅴ, Ⅱ - Ⅵ family and Ⅳ compounds or elemental semiconductors doped with transition metal elements to get. Mn-doped
GaAs is the most studied and most detailed study of the system, the Curie temperature is currently up to 185K. Their magnetic properties from the carrier (hole)-induced
Ferromagnetic exchange interaction between the doped Mn ions mediated by holes generated macro-ferromagnetic exchange interaction resulting in spontaneous
Polarization. However, due to its Curie temperature is still too low at room temperature application. Therefore, the search for Curie temperature at room temperature or above room temperature magnetic
Applied research of semiconductor materials to become a hot issue. Theory predicts, Ge-based magnetic semiconductors above the Curie temperature up to 400K, ZnO
Based magnetic semiconductors above the Curie temperature up to 300K. In addition, as the semiconductor itself, Ge with the current mature phase of Si-based semiconductor technology
Compatible, ZnO semiconductor light-emitting materials, piezoelectric materials, transparent conductive film has a broad research and application, so, Ge-based and ZnO-based
Magnetic semiconductors has been of great concern! At present, research work from the point of view, Ge-based and ZnO-based magnetic semiconductors are
Needed to overcome a series of common problems, such as: the nature of the sample preparation method and often depends on the growth process, each sample of magnetic
Sexual expression is not consistent with the origin of ferromagnetism is no uniform interpretation and so on. To solve these problems, we will use the low-temperature molecular beam epitaxy and
The sample was prepared by amorphous phase two experimental preparation methods, to study the Ge-based and ZnO-based http://www.everbeenmagnet.com/en/products/110-sintered-neodymium-magnets magnetic semiconductors. Which the low-temperature molecular beam epitaxy
Single-crystal samples prepared in the structure of its unity and purity of the composition can effectively prevent precipitation of the ferromagnetic impurity phase or
Ferromagnetic material of the sample sources of interference, more conducive to analysis of its magnetic origin and so on; and amorphous phase approach is from the application point of view
, By increasing the solubility of ferromagnetic metals to increase the Curie temperature and magnetization. This thesis work includes preparation of single crystal, amorphous
Ge-based and ZnO-based magnetic semiconductor thin films, to study its magnetic and transport properties, and its corresponding magnetic transport mechanism of the origin and
. Paper's results are as follows: ● We use ultra-high vacuum molecular beam epitaxy at low temperature the Ge_ (1-x) Mn_x
(X = 0.019,0.041,0.051,0.072,0.105) diluted magnetic semiconductor thin films, and studied its magnetic and transport properties. Real-time reflection
High-energy electron diffraction image (RHEED) and XRD measurements show that when the Mn content x less than 0.105, Ge_ (1-x) Mn_x film to maintain crystal structure.
5K hysteresis whirl under the line that all samples are ferromagnetic, in addition to single crystal film in the presence of strong magnetic anisotropy, that is, magnetization in the
Film plane and perpendicular to the membrane surface is very different, indicating that there is a strong film spin-orbit coupling. R-T curve shows that the film
Conductive properties are semiconducting properties, and low-temperature region in line with Efros variable range transport transition. Ge_ (0.949) Mn_ (0.051) film
The Hall effect measurements showed that the Hall effect and anomalous Hall effect from the normal Hall effect composition. Anomalous Hall effect shows that the sample
Ferromagnetism by the carrier to pass. As the temperature decreases, the coefficient of the normal Hall effect changes sign occurs. According to Emin's theory, the jump
Hall moved to have conductive areas of the Aharonov-Bohm effect ring contains an odd number of bits will be sign anomaly, given the low sample
Conductive zone of transition, we believe that the distribution of low temperature in any of the three local Mn acceptor transition between the centers of the anomalous Hall effect
Sources, but also the normal Hall effect changes sign from. ● We have three different conductivity types (n-type, intrinsic, p-type) Ge single
Crystal substrate, molecular beam epitaxy epitaxy of Ge_ (1-x) Mn_x single crystal film, to form Ge_ (1-x) Mn_x / Ge heterojunction, and research
The heterojunction rectification characteristics and magnetic field characteristics of its rectification. Research shows that all samples have the rectification effect results, which
the best characteristics of pn junction rectifier, pp knot by the maximum current density and magnetic field of the pi junction control the most obvious. In addition, in view of p-i junction
To the positive magnetoresistance observed, its value as the temperature rises in the 225K A great value, combined with the band filling effect and the magnetic field resulting wave function
Contraction effect on the experimental results to make a more reasonable explanation. ● We use molecular beam epitaxy of ultra-high vacuum and low sample stage
Temperature growth conditions in liquid nitrogen cooled glass substrates were prepared by high Mn concentrations Ge_ (1-x) Mn_x (x = 0.39,0.52,0.66,0.79) non-
Crystal magnetic semiconductor thin films, and studied its magnetic and transport aspects of nature. All samples under 5K whirl lines indicate magnetic hysteresis and
Coexist in the sample being paramagnetic. Ge_ (0.48) Mn_ (0.52) film, the Curie temperature up to 220K. X = 0.66 and 0.79 in the sample
Are observed in exchange bias phenomenon, combined with the corresponding structural properties of thin films, this phenomenon may come from poor areas of the ferromagnetic phase-Mn and Mn-rich
Area and Mn_ (11) Ge_8 antiferromagnetic phase-antiferromagnetic exchange coupling between the role. Conductive properties of the sample electrical properties of semiconductors, in temperature
Degrees below the Curie temperature of the sample to the anomalous Hall effect observed, indicating that the ferromagnetism is caused by carrier. ● We
Using oxygen plasma assisted molecular beam epitaxy source was prepared at room temperature ferromagnetism with the Co doped ZnO diluted magnetic semiconductor single crystal film. Real
Observed when the scan shows RHEED and XRD 2θ Zn_ (1-x) Co_xO film is single crystal. Transmission spectrum and XPS measurements indicate that Co in Co ~
(2 +) chemical state. SQUID measurements show Zn_ (1-x) Co_xO thin films with room temperature ferromagnetism, the Curie temperature above room
Temperature, the saturation magnetization increases with Co doping increases. Combining these results can determine the sample at room temperature ferromagnetism is the
Sign of. The magnetic origin can be used to describe the bound magnetic polaron model, the doping of Co ~ (2 +) to produce light as a medium of exchange donor defects
Role in forming a magnetic polaron, as a result of these magnetic polaron coupling between the interaction of a long-range ferromagnetic order to form a macro
View of ferromagnetism. In addition, the conductive properties of the sample electrical properties of semiconductors. ● We have studied the sputtering device obtained by the non-uniform
High quality Fe concentration Zn_ (1-x) Fe_xO magnetic semiconductor thin films annealed state and the magnetic and transport aspects of nature. Study Table
Ming, their magnetic properties by controlling the composition of the heterogeneity and to be modulated by rapid annealing. Ferromagnetic and paramagnetic elements coexist in
Preparation of state Zn_ (1-x) Fe_xO film samples, and in the preparation of state Zr_ (0.23) Fe_ (0.77) O thin films observed positive reversal
Field, indicating that local neighbor ferromagnetic films with antiferromagnetic coupling region, this role is to stimulate the transition from the hot-carrier passed by, the
Reverse field size 110K to 300K temperature range increases with increasing temperature. Degree Year: 2009