胡志高
凝聚态光电子材料、器件与物理;半导体材料及其低维结构的光学与电子性质;铁电以及铁磁极化材料的光电特性等。
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- 姓名:胡志高
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学术头衔:
博士生导师, 教育部“新世纪优秀人才支持计划”入选者
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学科领域:
制糖技术
- 研究兴趣:凝聚态光电子材料、器件与物理;半导体材料及其低维结构的光学与电子性质;铁电以及铁磁极化材料的光电特性等。
胡志高,男,1975 年 10 月生,理学博士。 华东师范大学教授,博士生导师。
2004年3月在中国科学院上海技术物理研究所获理学博士学位。2004年3月至2007年2月分别在美国佐治亚州州立大学(Georgia State University)和德国海德堡大学(University of Heidelberg)从事博士后研究工作。2007年4月起任华东师范大学信息科学技术学院教授。在铁电薄膜、III-V族半导体以及稀磁氮化合物等宽禁带材料的光电特性研究方面取得了一系列的创新成果。系统性地开展了铁电薄膜材料光学性质的研究;首次研究了稀磁III-N族半导体的红外声子模式以及光学各向异性响应行为,比较系统地解释了三元氮化合物中掺杂浓度对自由载流子与纵向声子耦合行为的影响;设计并实现了红外椭圆偏振光谱对单分子自组织有机薄膜的探测等。发表SCI收录国际学术刊物论文40多篇,出版国际英文学术专著章节1章。胡志高教授是德国洪堡学者,兼任《Physical Review B》等国际著名学术期刊的审稿人。
主要研究领域:凝聚态光电子材料、器件与物理;半导体材料及其低维结构的光学与电子性质;铁电以及铁磁极化材料的光电特性等。实验室目前配备有先进的傅立叶红外光谱仪、紫外-近红外分光光度计、显微拉曼及荧光光谱仪、椭圆偏振光谱仪以及各种低温测量系统等。
目前承担的主要研究项目:1.上海市浦江人才培养计划项目:“宽带隙铁电薄膜材料及其纳米结构的光电性能研究”(2007.10-2009.9) 2.973国家重大研究计划项目:“半导体量子结构中的自旋量子调控”(2007.7-2012.6)。
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【期刊论文】Infrared spectroscopic ellipsometry of (Pb, La) (Zr, Ti) O3 thin films on platinized silicon
胡志高, Z.G. Hu ∗, F.W. Shi, T. Lin, Z.M. Huang, G.S. Wang, Y.N. Wu, J.H. Chu
Physics Letters A320(2004)478-486,-0001,():
-1年11月30日
Lead lanthanum zirconate titanate (PLZT) thin films with different La concentrations (x), whose composition is x/40/60, have been grown directly on Pt/Ti/SiO2/Si (100) substrates by a modified sol-gel method. X-ray diffraction analysis shows that the PLZT thin films are polycrystalline. The infrared optical properties of the PLZT thin films have been investigated using the infrared spectroscopic ellipsometry in the spectral range of 2.5–12.5 μm. By fitting the measured ellipsometric spectra (Ψ andΔ) with a three-phase model (air/PLZT/Pt), and a derived classical dispersion relation for the thin films, the optical constants and thicknesses of the thin films have been obtained. The refractive index of the PLZT thin films decreases with increasing La concentrations, however, the extinction coefficient increases with increasing La concentrations except for the PLZT(4/40/60) thin films. The values of the effective static charge calculated for the PLZT thin films, which state that PLZT belongs to a mixed ionic-covalent compound, decrease with increasing La concentrations. Moreover, the refractive index at the wavelength of 2.5 μm changes linearly with the effective static charge. The plot of the calculated infrared optical absorption versus wavelength for the Ni/PLZT/Pt multilayer structures with various La concentrations is given and indicates that the PLZT thin films are excellent candidates for ferroelectric infrared detectors and focal plane arrays.
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胡志高, Z.G. HU F.W. SHI Z.M. HUANG Y.N.WU G.S.WANG J.H. CHU
Appl. Phys. A80, 841-846(2005),-0001,():
-1年11月30日
(Pb1−xLax)Ti1−x/4O3 (PLT) ferroelectric thin films with various La concentrations have been grown on LaNiO3/Si(100) substrates by a modified sol-gel technique. X-ray-diffraction analyses show that the PLT and LaNiO3 thin films are polycrystalline and entirely perovskite phase. The infrared optical properties of the PLT thin films have been investigated using infrared spectroscopic ellipsometry in the wavelength range of 2.5-12.5 μm. By fitting the measured ellipsometric parameter (tanΨ and cos Δ) data with a four-phase model (air/PLT/LaNiO3/Si), and a derived dispersion relation for the PLT thin films, the optical constants and thicknesses of the thin films have been determined. The refractive index of the PLT thin films decreases with increasing wavelength; however, by a Kramers-Kronig analysis the extinction coefficient increases with increasing wavelength. Moreover, the refractive index and extinction coefficient of the PLT thin films increase with increasing La concentration. This indicates that the infrared optical constants of the PLT thin films are a function of the La concentration. It is believed that the increase in the infrared optical constants of the PLT thin films with increasing La concentration is mainly due to the crystallinity and the electronic band structure of the PLT thin films.
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胡志高, Z.G. Hu and A.G.U. Perera a), Y. Paltiel, A. Raizman, and A. Sher
,-0001,():
-1年11月30日
The reflectance measurements of p-type GaSb: Zn epitaxial films with different hole concentrations, grown by metalorganic vapor-phase epitaxy, have been investigated in the 3-30-THz frequency region. The experimental spectra were fitted using a classical harmonic Lorentz oscillator and the Drude model, illustrating that the hole effective mass and the mobility change with the carrier concentration. The hole effective mass was found to vary from 0.22m to 0.41m as the carrier concentration changed from 3.5×1017 to 3.8×1018 cm−3. The mobility values derived from the reflectance measurements were slightly smaller than the values obtained from Hall-effect measurements. A sublinear relationship between the absorption coefficient and the hole concentration was found at a frequency of 3 THz. Those results can be used for designing GaSb-based terahertz detectors.
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胡志高, Z.G. Hu, M. Strassburg, , N. Dietz, A.G.U. Perera, * A. Asghar, and I.T. Ferguson
,-0001,():
-1年11月30日
The optical properties of hexagonal AlxGa1−xN x from 0.05 to 0.42 epitaxial films with Sim doping concentrations up to 1018 cm−3 grown on c-plane sapphire substrates by metal-organic chemical vapor deposition have been investigated using infrared reflectance spectra. The dielectric functions=1+i2 of the AlxGa1−xN films are determined in the wavelength region of 1.54-50m at room temperature. The experimental reflectance spectra are analyzed using classical harmonic Lorentz oscillators and Drude model in the transparent,reststrahlen, and free carrier absorption regions. GaN-like E1 transverse-optical TO phonon frequency linearly decreases and its strength increases with decreasing Al composition. However, AlN-like E1 TO phonon frequency shows a relatively weak composition dependence and its strength increases with increasing composition. At a wavelength of 1.54m, 1 varies between 4.86 and 5.2 when the composition changes from 0.05 to 0.42 and 2 is close to zero. The longitudinal-optical phonon plasmon LPP coupled modes of n-type hexagonal AlxGa1−xN films are also discussed. For samples with higher concentrations beyond 1018cm−3 the upper LPP coupled mode frequencies increase with increasing carrier concentration indicating the transition from phononlike to plasmonlike behavior.
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胡志高, Z.G. Hu, a, M.B.M. Rinzan, A.G.U. Perera, b, Y. Paltiel, A. Raizman, A. Sher, and M. Zhu, c
Eur. Phys. J. B 50, 403-410 (2006),-0001,():
-1年11月30日
Reflectance measurements from p-type GaSb: Zn epitaxial films with different hole concentrations(1017-1018 cm−3) have been investigated over the frequency region of 100-1000 cm−1. A minimum broadening feature corresponding to the hole plasmon was observed in the reflectance spectra. The experimental infrared spectra were well fitted using a Lorentz-Drude dispersion model. The real part ε1 of the dielectric function decreases with increasing hole concentration. However, the imaginary part ε2 increases with hole concentration in the far-infrared region. This indicates that the acoustic- and optic-phonons mainly participate in the free carrier absorption processes. The hole mobility obtained from Hall-effect measurements is slightly larger than that derived from optical measurements and the average ratio of mobilities is estimated to be 1.33. Owing to overdamping effects, the upper branch of longitudinal-optical phonon plasmon (LPP) coupled modes was observed. The upper LPP+ frequency increases with hole concentration and it shows a transition from phonon-like to plasmon-like behavior. A theoretical analysis with solutions in the complex frequency plane describes these experimental results.
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【期刊论文】Infrared Spectroscopic Ellipsometry of n-Alkylthiol (C5-C18) Self-Assembled Monolayers on Gold
胡志高, Z.G. Hu, P. Prunici, P. Patzner, and P. Hess*
J. Phys. Chem. B2006, 110, 14824-14831,-0001,():
-1年11月30日
The infrared spectroscopic ellipsometry (IRSE) of n-alkylthiol (CH3(CH2)xSH, x ) 4, 6, 7, 8, 10, 13, 15, and 17, self-assembled monolayers (SAMs), with 5-18 carbon atoms (C5-C18), grown on gold-coated Si(100) substrates) was investigated at room temperature. The C-H stretching vibrations could be resolved even for pentathiol, the shortest chain studied. The symmetric and asymmetric stretching vibrations of the CH2 groups are located at about 2850 and 2920 cm-1, and those of CH3 are at about 2877 and 2962 cm-1, respectively; they show a slight shift with the number of CH2 units. In addition, Fermi resonance of the symmetric CH3 stretching vibration at 2940 cm-1 appears with decreasing chain length due to weak coupling with the asymmetric CH2 stretching vibration. The "odd-even effect" of the n-alkylthiol SAMs with varying CH2 units could be distinguished by the two interactive IRSE parameters. The relative ellipsometric spectra for the four longest chains could be reproduced quite well by using a Lorentz multioscillator model with a threephase optical model (air/SAMs/gold). On the basis of the theoretical calculations, the vibrational strength of these oscillators is very weak, its magnitude being 10-4-10-5. The full width at half-maximum (fwhm) of the peaks varies from 7 to 33 cm-1. Moreover, the intensity of the C-H vibrations increases with the number of methylene units, due to strong lateral interactions and ordering effects occurring for longer chains.
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【期刊论文】Optical constants and thermo-optic coefficients of nanocrystalline diamond films at 30-500℃
胡志高, Z.G. Hu and P. Hess a)
,-0001,():
-1年11月30日
The refractive index and absorption index of nanocrystalline diamond NCD films were investigated using spectroscopic ellipsometry between 30 and 500℃. Due to their high transparency the experimental spectra could be well fitted in the subgap region using a single-oscillator model with a four-phase layered structure. The single-oscillator model yields a small optical absorption in the band gap region. The temperature dependence of dispersion of the refractive index over the photon energy range of 1.15-4.75V was determined. Based on the Bose-Einstein model, a thermo-optic coefficient of 1/n n/T=6.5 10−6 K−1 at 300 K was obtained for the NCD film in the near-infrared region.
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胡志高, Z.G. Hu, A.B. Weerasekara, N. Dietz, A.G.U. Perera, , * M. Strassburg, M.H. Kane, A. Asghar, and I.T. Ferguson
,-0001,():
-1年11月30日
Optical anisotropy of hexagonal Ga1−xMnxN(x from 0.0% to 1.5%) epitaxial films grown on c-plane sapphire substrates has been investigated using far- and mid-infrared s- and p-polarized reflectance spectra at oblique incidence at 10, 22, and 32, respectively. The experimental data at room temperature can be well reproduced simultaneously in the measured frequency region of 200-2000 cm−15-50 m, which was based on a four-phase layered system using a 4×4 matrix method M. Schubert, Phys. Rev. B53, 4265(1996). The lattice vibrations perpendicular and parallel to the optic c axis(E1 and A1 modes) were expressed by Lorentz oscillator dielectric function model. There was a striking absorption dip at the A1 phonon frequency in p-polarized reflectance spectra due to the optical anisotropy. These infrared-active phonon parameters were obtained with uniaxial dielectric tensor. It was found that the A1 longitudinal-optical phonon frequency linearly increases with the Mn composition for the diluted magnetic semiconductor epilayers. The broadening values of the A1 phonon changed from 3.6±1.3 to 9.0±1.6 cm−1, showing the high film crystal quality. Moreover, the ordinary and extraordinary dielectric functions ε⊥ and ε‖ of the epilayers were determined. It indicated that was larger than ε⊥ for the Ga1−xMn x N films in the reststrahlen region, which can be ascribed to slight structural degradation of the wurtzite lattice.
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胡志高, Z.G. Hu, a) Y.W. Li, F.Y. Yue, and Z.Q. Zhu, J.H. Chu
,-0001,():
-1年11月30日
Optical properties of ferroelectric Bi3.25La0.75Ti3O12 BLT films on quartz have been investigated using ultraviolet-infrared transmittance spectra in the temperature range of 77-500 K. The spectra can be divided into three distinctive photon regions between 1.1 and 6.5V. It is found that the band gap Eg decreases from 3.88 to 3.77V with the temperature. The parameters aB and B of the Bose-Einstein model are 30.3V and 218.7K, respectively. The band narrowing coefficient dEg/dT is −2.65 10−4V/K at room temperature. The present results can be crucial for future application of ferroelectric BLT-based electro-optic and high temperature optoelectronic devices.
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【期刊论文】Properties of highly(100)oriented Pb(Mg1/3,Nb2/3)O3-PbTiO3 films on LaNiO3 bottom electrodes
胡志高, Y.W. Li, a) Z.G. Hu, and F.Y. Yue, G.Y. Yang and W.Z. Shi, X.J. Meng and J.L. Sun, J.H. Chu
,-0001,():
-1年11月30日
The 70%Pb Mg1/3, Nb2/3O3-30%PbTiO3 PMNT films have been fabricated on LaNiO3 LNO coated silicon substrate. The conductive LNO films act as a seed layer for the growth of PMNT films, which depresses the formation of pyrochlore phase and induces the high 100 preferred orientation of perovskite PMNT films. Compared with the PMNT films grown on platinum bottom electrode, the ferroelectric properties of PMNT films grown on LNO are enhanced. The frequency dependence of complex permittivity from PMNT films on LNO is the conjunct result of polarization relaxation and movement of oxygen vacancy, which can be fitted by the function containing Debye and universal dielectric response models, respectively.
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