Investagetion Of Structure,Transport And Magnetic Properties Of Diluted Magnetic Semiconductors SiC/Cu Ulrtrathin Multilayer

Diluted magnetic semiconductor possessing the electrical and spinning properties has gained great interests for its potential technological applications in spintronic devices.SiC based dilute magnetic semiconductor has attracted much attention dueing to that SiC posesses good electrical conductivity,high thermal conductivity and high saturation electron drift velocity.In this paper,SiC/Cu ultrathin multilayer films with periodical structure were prepared through alternating rf and dc magnetron sputtering.On one hand,nonmagnetic dopant Cu effectively avoid the second magnetic phase from the magnetic elements to the intrinsic magnetic,on the other hand,by alternate deposition,increasing the contact area of SiC and Cu can improve Cu doping concentration,then improve saturation magnetization.This paper states of the influence of the Cu layer thickness and annealing temperature on the structure,transport and magnetism of multilayer films.It is rarely reported about SiC/Cu multilayer research.For the as-deposited multilayer film of different Cu layer thickness,XRR pattern indicates that the films are of a periodical multilayer structure.ATR-FTIR spectra indicate The SiC layers of films is the amorphous structure embedded crystalloid clusters.XPS spectra indicate the existence of Si-C bond and Cu enters SiC with Cu+ valance state in the films.XAFS spectra prove the Cu atoms are incorporated into SiC and substituted for Si sites.The PL spectra proved the structure of SiC in form of ultra small nano crystal.The luminescence peak located in around 437 nm is attributed to the SiC nano crystal.All the multilayer films showed the characteristic of p-type semiconductor.The carrier concentrition of the multilayer films are of the order of 1020,Mott variable range hopping mainly dominates the conduction mechanism of the films.The M-H curves indicates that all the films shows room temperature ferromagnetism and the saturation magnetization reaches to 12.14 emu/cm3 with the decreasing thickness of Cu layer.The theoretical fitting of magnetic resistance and the calculation of state density proved that the ferromagnetism of multilayer films origins from the carrier-mediated p-d(Cu 3d and C 2p)exchange interaction and the p-d exchange interaction became weaker with the increase of Cu layer thickness.The multilayer films were annealed at different temperature in vacuum condition.The SiC layers are the amorphous structure which crystalloid clusters were embedded.A part of Cu in Cu layers coupled into the SiC and substituted for Si sites in the form of mixed valence statesCu,Cu+ and Cu2 +.The PL spectra proved the structure of SiC in form of ultra small nano crystal.The luminescence peak located in around 437 nm is attributed to the SiC nano crystal.All the multilayer films showed the characteristic of p-type semiconductor and room temperature ferromagnetism.Mott variable range hopping mainly dominates the conduction mechanism of the films.Hall effect indicated that resistivity increases with the increasing annealing temperature,carrier concentration Pc and saturation magnetization Ms decreased with the increasing of annealing temperature.It shows that the ferromagnetism origins from carrier mediate p-d exchange effect.The annealed multilayer films showed a giant magnetoresistance(GMR)effect,it is rarely reported.The mechanism may be induced by the combined impact of positive and negative MR.The effect of the negative MR is caused by weak localization of electrons in low temperature and positive MR is caused by the shrinkage of carrier wave function.