借助典型的固相反应烧结机制，研究了MgO含量对微波高品质因数瓷介材料微观结构与介电性能参数影响的规律。结果表明：高温烧结的镁钛系瓷介质中，随着MgO含量增加，Mg 2 TiO 4晶相的含量逐渐降低、瓷体晶粒由尖晶石型演变为氯化钠型结...借助典型的固相反应烧结机制，研究了MgO含量对微波高品质因数瓷介材料微观结构与介电性能参数影响的规律。结果表明：高温烧结的镁钛系瓷介质中，随着MgO含量增加，Mg 2 TiO 4晶相的含量逐渐降低、瓷体晶粒由尖晶石型演变为氯化钠型结构，对应的微波介电常数出现缓慢降低，在10.10~13.37范围连续可调。当x=16时，在1525℃/2 h烧成，可获得性能优良的（2＋x）MgO-TiO2陶瓷，其ρ=3.49g·cm–3，εr=10.37，Q·f=118747 GHz（f=10.47 GHz），τf=–53.35×10–6℃–1。展开更多
The p-type doping efficiency of 4 H silicon carbide(4 H-SiC)is rather low due to the large ionization energies of p-type dopants.Such an issue impedes the exploration of the full advantage of 4 H-SiC for semiconductor...The p-type doping efficiency of 4 H silicon carbide(4 H-SiC)is rather low due to the large ionization energies of p-type dopants.Such an issue impedes the exploration of the full advantage of 4 H-SiC for semiconductor devices.In this study,we show that co-doping group-IVB elements effectively decreases the ionization energy of the most widely used p-type dopant,i.e.,aluminum(Al),through the defect-level repulsion between the energy levels of group-IVB elements and that of Al in 4 H-SiC.Among group-IVB elements Ti has the most prominent effectiveness.Ti decreases the ionization energy of Al by nearly 50%,leading to a value as low as~0.13 eV.As a result,the ionization rate of Al with Ti co-doping is up to~5 times larger than that without co-doping at room temperature when the doping concentration is up to 10^(18)cm^(-3).This work may encourage the experimental co-doping of group-IVB elements such as Ti and Al to significantly improve the p-type doping efficiency of 4 H-SiC.展开更多
基金Project supported by the National Key Research and Development Program of China(Grant Nos.2017YFA0205704 and 2018YFB2200101)the National Natural Science Foundation of China(Grant Nos.91964107 and 61774133)+2 种基金Fundamental Research Funds for the Central Universities,China(Grant No.2018XZZX003-02)the National Natural Science Foundation of China for Innovative Research Groups(Grant No.61721005)Zhejiang University Education Foundation Global Partnership Fund。
文摘The p-type doping efficiency of 4 H silicon carbide(4 H-SiC)is rather low due to the large ionization energies of p-type dopants.Such an issue impedes the exploration of the full advantage of 4 H-SiC for semiconductor devices.In this study,we show that co-doping group-IVB elements effectively decreases the ionization energy of the most widely used p-type dopant,i.e.,aluminum(Al),through the defect-level repulsion between the energy levels of group-IVB elements and that of Al in 4 H-SiC.Among group-IVB elements Ti has the most prominent effectiveness.Ti decreases the ionization energy of Al by nearly 50%,leading to a value as low as~0.13 eV.As a result,the ionization rate of Al with Ti co-doping is up to~5 times larger than that without co-doping at room temperature when the doping concentration is up to 10^(18)cm^(-3).This work may encourage the experimental co-doping of group-IVB elements such as Ti and Al to significantly improve the p-type doping efficiency of 4 H-SiC.
