Arsenic can diffuse into high-κ dielectrics during OaAs-based metal oxide semiconductor transistor process, which causes the degradation of gate dielectrics. To explore the origins of the degradation, we employ nonlo...Arsenic can diffuse into high-κ dielectrics during OaAs-based metal oxide semiconductor transistor process, which causes the degradation of gate dielectrics. To explore the origins of the degradation, we employ nonlocal B3LYP hybrid functional to study arsenic related defects in ZrO2. Via band alignments between the OaAs and ZrO2, we are able to determine the defect formation energy in the GaAs relative to the ZrO2 band gap and assess how they will affect the device performance. Arsenic at the interstitial site serves as a source of positive fixed charge while at the oxygen or zirconium substitutional site changes its charge state within the band gap of GaAs. Moreover, it is found that arsenic related defects produce conduction band offset reduction and gap states, which will increase the gate leakage current.展开更多
The electronic structures and optical properties of the monoclinic ZrO2 (m-ZrO2) are investigated by means of first-principles local density approximation (LDA) + U approach.Without on-site Coulomb interactions,the ba...The electronic structures and optical properties of the monoclinic ZrO2 (m-ZrO2) are investigated by means of first-principles local density approximation (LDA) + U approach.Without on-site Coulomb interactions,the band gap of m-ZrO2 is 3.60 eV,much lower than the experimental value (5.8 eV).By introducing the Coulomb interactions of 4d orbitals on Zr atom (Ud) and of 2p orbitals on O atom (Up),we can reproduce the experimental value of the band gap.The calculated dielectric function of m-ZrO2 exhibits a small shoulder at the edge of the band gap in its imaginary part,while in the tetragonal ZrO2 and cubic ZrO2 it is absent,which is consistent with the experimental observations.The origin of the shoulder is attributed to the difference of electronic structures near the edge of the valence and conduction bands.展开更多
The stability, infrared spectra and electronic structures of （ZrO2）n （n= 3--6） clusters have been investigated by using density-functional theory （DFT） at B3LYP/6-31 G＊ level. The lowest-energy structures have ...The stability, infrared spectra and electronic structures of （ZrO2）n （n= 3--6） clusters have been investigated by using density-functional theory （DFT） at B3LYP/6-31 G＊ level. The lowest-energy structures have been recognized by considering a number of structural isomers for each cluster size. It is found that the lowest-energy （ZrO2）5 cluster is the most stable among the （ZrO2）n （n=3--6） clusters. The vibration spectra of Zr-O stretching motion from terminal oxygen atom locate between 900 and 1000 cm 1, and the vibrational band of Zr---O--Zr--O four member ring is obtained at 600~700 cm ^-1, which are in good agreement with the experimental results. Mulliken populations and NBO charges of （ZrO2）n clusters indicate that the charge transfers occur between 4d orbital of Zr atoms and 2p orbital of O atoms. HOMO-LUMO gaps illustrate that chemical stabilities of the lowest-energy （ZrO2）,, （n = 3--6） clusters display an even-odd alternating pattern with increasing cluster size.展开更多
基金Supported by the Key Project of Education Department of China under Grant No 211035the Science Foundation from Education Department of Liaoning Province under Grant No L2014445
文摘Arsenic can diffuse into high-κ dielectrics during OaAs-based metal oxide semiconductor transistor process, which causes the degradation of gate dielectrics. To explore the origins of the degradation, we employ nonlocal B3LYP hybrid functional to study arsenic related defects in ZrO2. Via band alignments between the OaAs and ZrO2, we are able to determine the defect formation energy in the GaAs relative to the ZrO2 band gap and assess how they will affect the device performance. Arsenic at the interstitial site serves as a source of positive fixed charge while at the oxygen or zirconium substitutional site changes its charge state within the band gap of GaAs. Moreover, it is found that arsenic related defects produce conduction band offset reduction and gap states, which will increase the gate leakage current.
基金the National Natural Science Foundation of China，the Strategic Programs for Innovative Research，the Computational Materials Science Initiative，the Yukawa International Program for Quark-Hadron Sciences at YITP,Kyoto University
文摘The electronic structures and optical properties of the monoclinic ZrO2 (m-ZrO2) are investigated by means of first-principles local density approximation (LDA) + U approach.Without on-site Coulomb interactions,the band gap of m-ZrO2 is 3.60 eV,much lower than the experimental value (5.8 eV).By introducing the Coulomb interactions of 4d orbitals on Zr atom (Ud) and of 2p orbitals on O atom (Up),we can reproduce the experimental value of the band gap.The calculated dielectric function of m-ZrO2 exhibits a small shoulder at the edge of the band gap in its imaginary part,while in the tetragonal ZrO2 and cubic ZrO2 it is absent,which is consistent with the experimental observations.The origin of the shoulder is attributed to the difference of electronic structures near the edge of the valence and conduction bands.
基金Project supported by the National Natural Science Foundation of China （No. 20876005） and the National Basic Research Program of China （No. 2010CB732301 ）.
文摘The stability, infrared spectra and electronic structures of （ZrO2）n （n= 3--6） clusters have been investigated by using density-functional theory （DFT） at B3LYP/6-31 G＊ level. The lowest-energy structures have been recognized by considering a number of structural isomers for each cluster size. It is found that the lowest-energy （ZrO2）5 cluster is the most stable among the （ZrO2）n （n=3--6） clusters. The vibration spectra of Zr-O stretching motion from terminal oxygen atom locate between 900 and 1000 cm 1, and the vibrational band of Zr---O--Zr--O four member ring is obtained at 600~700 cm ^-1, which are in good agreement with the experimental results. Mulliken populations and NBO charges of （ZrO2）n clusters indicate that the charge transfers occur between 4d orbital of Zr atoms and 2p orbital of O atoms. HOMO-LUMO gaps illustrate that chemical stabilities of the lowest-energy （ZrO2）,, （n = 3--6） clusters display an even-odd alternating pattern with increasing cluster size.
