The Research Of Mn-doped Group-Ⅳ Semiconductor

In modern information technology,data processing is based on the control of the charge of the carriers and the information storage technique uses spins of the carriers. The use of carriers spin and charge simultaneously appears promising for a new class of devices such as chips that integrate memory and microprocessor functions.The control of spin-dependent phenomena in conventional semiconductors may lead to many novel properties,such as colossal magneto-resistance,magneto-optical effect, etc.So there is interest in developing magnetic semiconductors which will exhibit ferromagnetism.Nowadays,the main method of fabricating ferromagnetic semiconductrs is to dope transition elements into semiconductors.There are two originations to realize spin polarization of carriers.The first is the double exchange interaction between transition ions which mediated by oxygen ion.The second is the strong interaction between the d electrons of transition ions and sp electrons of the main semiconductors,which leads to the splitting of semiconductors' conducting band. Thus,spin majority and spin minority are formed,and carriers are spin polarized.The traditional semiconductor industry is based on the Si materials,and therefore the magnetic semiconductors basing on the Si and Ge materials are much easier to be integrated into the modern semiconductor industry and show extensive application values.According to the existing theoretical predictions,the Curie temperature of Mn_xGe_1-x can reach 400K.The investigation on groupⅣdiluted magnetic semiconductors have been developing since 2002,when Park and other authors reported the diluted Mn_xGe_1-x magnetic semiconductors with Curie temperature between 25K and 116K and found that the hole-induced ferromagnetic order in films can be controlled by applied electronic-field,which makes the applications possible. As the basic semiconductor materials in main-stream microelectronic industry,the Si materials with high quality are low in productive costs.More important,they are compatible with the present mature microelectronic technology.Up to now,various results have been reported.In 2004,Zhang et al prepared the Si_0.95Mn_0.05 samples on the single crystalline Si and after crystallization treatment,the ferromagnetism continues to 400K.In 2005,M.Bolduc,C.Awo-Affouda et al prepared samples by ion implantation and found that annealing has great influence on ferromagnetism.Any way,preparing Si_1-xMn_x by magnetron sputtering has made little progress till now.In order to get the samples with best quality,we fabricate the Si_1-xMn_x films with high Mn concentration as well as the ones with low Mn concentration respectively by sputtering.We prepared samples with concentration from five percent to fifty percent by magnetron sputtering.During the growth process,the glass substrate was cooled by water.From the AFM and SEM analysis,the sample grows extremely unformly, proved that in the growth process intense diffusion occured btween Mn and Si. Moreover,the low temperature growth is a non-equilibrium process,enables Mn to have a higher solubility in Si.According to the magnetic and transportation measurements,the samples show superparamagnetism at low temperature,which may be caused by Mn-clusters in the samples.After annealing,they show ferromagnetism at room temperature.The R-T characters of the samples reveal that they are semiconductors.The relationship between lnR～T^-1/2 shows that under 24K,the conductive mechanism of the samples is variable-range hopping while between 52K and 72K,it is the thermal activated model. Between 24K and 52K,both of the conductive mechanisms contribute to the conductivity.In addition,the samples only show ordinary hall effect at room temperature and the coefficients of hall effect change from positive to negative with the concentration of Mn to identify the change of the types of carriers.The magnetic properties of the samples at room temperature show that ferromagnetism is easier to get by doping less Mn.