Ni掺杂浓度对CdS:Ni体系电子和光学性质的影响

采用基于密度泛函理论框架下的第一性原理计算方法,对纤锌矿结构CdS:Ni的几何结构、能带结构、电子态密度和光学性质随Ni掺杂浓度的变化进行了系统地研究。计算结果显示,无论是在富镉,还是富硫条件下,计算得到不同Ni掺杂浓度的形成能都较小,说明CdS:Ni系统在实验上是可以实现的;Ni掺杂的CdS在价带顶附近出现杂质带,大大提高了材料的导电率。光学性质的计算结果显示,Ni掺杂后体系的光学性质有很大的改变,在吸收光谱上产生了新的吸收峰,并且随着掺杂浓度的增加,吸收范围增大。所有结果表明,CdS:Ni体系是极具潜力的透明导电材料。     

掺杂Nd对ZnO电子结构和光学性质的影响

研究分析了Nd掺杂对ZnO体系的电子结构和光学性质的影响;根据密度泛函理论(DFT),采用第一性原理平面波超软赝势方法,对Nd掺杂的ZnO晶体结构进行几何优化,并计算体系的能带结构、总态密度、分波态密度、光学性质;结果表明,掺杂后体系晶格常数增大,带隙变宽,费米能级进入导带,介电常数、吸收系数发生较大变化;Nd是一种有效的ZnO体系施主掺杂元素;Nd的掺入提高了ZnO体系的导电性能,改善了光学性能。     

过渡金属掺杂单层MoS_2的第一性原理计算

利用基于密度泛函理论的第一性原理平面波赝势方法分别计算了本征及过渡金属掺杂单层MoS_2的晶格参数、电子结构和光学性质。计算结果显示,过渡金属掺杂所引起的晶格畸变与杂质原子的共价半径有联系,但并不完全取决于共价半径的大小。分析能带结构可以看到,Co、Ni、Cu、Tc、Re和W掺杂使能带从直接带隙变成了间接带隙。除了Cr和W以外,其它掺杂体系的禁带区域都出现了数目不等的新能级,这些杂质能级主要由杂质的d、S的3p和Mo的4d轨道组成。掺杂对MoS_2的光学性质也产生了相应的影响,使MoS_2的静态介电常数、介电函数虚部峰值、折射率和光电导率峰值呈现不同程度的增加。     

基于第一性原理计算的ΙA族元素掺杂p型ZnO光电学特性研究

采用基于密度泛函理论(DFT)的第一性原理平面波超软赝势方法计算了Li、Na、K掺杂ZnO纤锌矿结构的晶格结构、电子结构(能带结构、态密度)和光学特性,计算结果表明,在掺杂Na或K的情况下,晶胞体积的计算值均略有增加,而掺杂Li的晶胞体积小于本征ZnO,原因可能是系统能量的减小导致晶胞体积的降低.Li、Na掺杂的ZnO...     

四面体掺杂尖晶石结构Co1-xRexCr2O4(Re=Li、Na、K、Rb)的电子结构和光学性质

采用基于密度泛函理论(DFT)的平面波超软赝势方法, 计算了CoCr₂O₄及Li、Na、K和Rb四面体掺杂CoCr₂O₄的基态结构、电子结构和光学性质。计算结果表明: 一价离子四面体掺杂都导致晶格有微小的畸变, 使体系的稳定性降低, Rb掺杂的体系最稳定; 电子态密度的计算结果表明: 掺杂体系的导带主要有Co-3d和Cr-3d轨道电子构成, 掺杂离子改变了CoCr₂O₄导带的电子结构, 主要引起了导带Co-3d态密度峰的下移, 随着掺杂浓度的增大, 费米能级进入价带更深; 光学性质计算表明: 掺杂体系的吸收光谱发生红移, 并在低能区有很强的吸收, 表明掺杂能极大地提高CoCr₂O₄对可见光的吸收和光催化效率。     

Sb掺杂闪锌矿GaAs电子结构和光学性质第一性原理研究

采用基于密度泛函理论(DFT)框架下广义梯度近似平面波超软赝势法,计算了不同浓度Sb掺杂闪锌矿GaAs体系GaAs1-xSbx(x=0,0.25,0.5,0.75,1)的电子结构和光学性质,包括能带、态密度、复介电函数和吸收系数。计算结果表明,Sb掺杂导致体系晶格常数线性增大,并使得体系导带和价带组成发生改变,禁带宽度呈二次多项式变化。随着掺杂浓度的增加,体系静态介电常数线性增大,吸收带边出现了明显的红移现象。分析了掺杂Sb诱发GaAs1-xSbx体系的电子和光学性质改变,为Sb掺杂闪锌矿GaAs在光电子学和微电子学方面的实际应用提供了一定的理论依据。     

利用第一性原理研究Ge:Si电子结构与光学性质

采用基于密度泛函理论的平面渡超软赝势方法和广义梯度近似,计算了掺杂Ge前后单晶Si中Si-Ge键的布居值、键长以及能带结构和态密度.计算结果表明,Ge掺杂后体系晶格常数发生变化,Ge-Si键变长,布居值及带隙宽度减小.还进一步研究了掺杂Ge后的光学性质,掺杂后静态介电常数值与纯Si相比有所增大,且吸收带宽变窄、吸收带边明显红移,并对这些掺杂诱导的材料物性变化进行了解释.     

Na掺杂对闪锌矿ZnS电子结构和光学性质的第一性原理浅析

采用基于密度泛函理论(DFT)的第一性原理方法,在广义梯度近似(GGA)框架下,研究了纯净闪锌矿ZnS-B3和Na掺杂ZnS后的晶体结构、电子结构和光学性质。详细分析了不同Na掺杂浓度对ZnS的晶格常数、电子态密度和能带结构的影响,讨论了费米能级附近的电子组态对ZnS光学性质的影响。结果表明,掺杂Na对ZnS光学性能有极大的影响,当Na离子掺杂浓度为6.25%(原子分数)时,表现出较好的综合光学性质;当掺杂浓度为12.5%(原子分数)时,体系有效负电荷离子浓度增加,S3p态穿过费米能面,引起S3p态电子产生跃迁,在低能量红外区域产生新介电峰,引起光吸收,降低了ZnS材料的透红外性能。理论预测结果与文献报道的实验结果相吻合。     

镍间隙掺杂硅纳米线电子结构的研究

采用基于密度泛函理论的第一性原理的方法,对[100]方向镍间隙掺杂硅纳米线结构的稳定性和电子性质进行了计算。计算结果表明Ni原子更喜欢占据硅纳米线内部六角形间隙位置;掺杂体系费米能级附近的电子态密度来源于Ni3d态电子的贡献;同时发现不同构型的Ni掺杂硅纳米线,其带隙不同,且与未掺杂硅纳米线相比,带隙普遍减小。     

Cd-O共掺杂ZnTe第一性原理计算

采用基于密度泛函理论的第一性原理平面波超软赝势方法计算了未掺杂,Cd、O单掺杂及Cd-O共掺杂ZnTe的几何结构、能带结构、态密度分布、光吸收谱和介电常数等性质。结果表明:掺杂后的ZnTe晶格常数发生变化,其中Cd掺杂的ZnTe晶格失配最大;三种掺杂均使ZnTe禁带宽度减小,并引入杂质能级,其中O掺杂和Cd-O共掺杂的ZnTe的禁带宽度变化较为明显,同时掺杂后ZnTe吸收带边出现不同程度的红移。     

Structural and optical characterization of Ni-doped CdS quantum dots

Ni-doped CdS quantum dots have been prepared by chemical precipitation technique. The X-diffraction results indicated that the particle size of Ni-doped CdS nanoparticles is smaller than that of undoped CdS and no secondary phase was observed. The average grain size of the nanoparticles is found to lie in the range of 2.7–4 nm. The compositional analysis results show that Cd, Ni, and S are present in the samples. HRTEM studies reveal that the average particle size of undoped and Ni-doped CdS quantum dots is 2 and 3 nm, respectively. Raman spectra shows that 1LO, 2LO, and 3LO peaks of the Ni-doped CdS samples are slightly red shifted when compared to that of undoped CdS. The absorption edge of Ni-doped CdS nanoparticles is found to shift towards the higher-wavelength (red shift) side when compared to that of undoped CdS and the band gap is observed to lie in the range of 3.79–3.95 eV. This band gap is higher than that of the bulk CdS and is due to quantum confinement effect present in CdS nanoparticles.     

Structural,optical and magnetic properties of Ba and Ni doped CdS thin films prepared by spray pyrolysis method

Pure, Barium and Nickel doped cadmium sulphide (CdS) thin films have been coated on glass substrates at 400?°C by spray pyrolysis technique. The prepared CdS and doped CdS thin films were analysed by various measurements such as X-ray diffraction (XRD), SEM, optical and Vibrating Sample Magnetometer (VSM). X-ray diffraction measurements show that the coated pure, Ba and Ni-doped CdS thin films belong to the cubic crystal structure with orientation preferentially along (111) direction. The average crystallite size of pure, Ba and Ni doped CdS thin films were determined as 31, 33 and 45 nm, respectively. The average dislocation density (δ) and stacking fault (SF) of pure, Ba and Ni doped CdS thin films were also determined. The surface morphology and elemental analysis of the thin films were determined by scanning electron microscopy and energy dispersive X-ray spectrum (SEM with EDAX). It is observed that the optical energy bandgap has been decreased from 2.43 to 2.1 eV due to the doping Ba. The luminescence spectrum shows a strong emission peak at 517 nm in the case of pure CdS thin film and a meager red shift has been observed due to the doping. VSM studies were employed to study the magnetic behaviour of Ba and Ni doped CdS thin films.     

尖晶石结构Ni掺杂ZnFe2O4纳米颗粒的性能表征

利用水热法成功合成了纯ZnFe2O4和不同含量Ni掺杂Zn1-xNixFe2O4纳米颗粒。采用X射线衍射(XRD)、高分辨透射电子显微镜(HRTEM)、选区电子衍射(SAED)、X射线能量色散分析(XEDS)、紫外可见吸收光谱(UV-Vis)、傅里叶变换红外光谱(FT-IR)和振动样品磁强计(VSM)等测试技术研究掺杂浓度对Zn1-xNixFe2O4(x=0,0.1,0.3,0.5)样品的晶体结构、形貌、光学性能和磁学性能的影响。结果表明:所制备的Zn1-xNixFe2O4纳米颗粒结晶良好,Ni2+以替代Zn2+的形式掺杂到ZnFe2O4晶格中,生成立方尖晶石结构ZnFe2O4。随着Ni含量的增加,晶粒尺寸增大,晶格常数发生收缩。样品的形貌呈不规则的椭球形,且颗粒大小比较均匀。红外光谱的吸收峰位置并没有随Ni掺杂浓度的增加而变化。Zn1-xNixFe2O4纳米晶的光学带隙随Ni掺杂浓度增加而增大,与相应块体相比发生蓝移。在室温下,纯ZnFe2O4纳米晶呈现超顺磁性,掺杂样品具有明显的铁磁性。     

Optical and magnetic properties of Ni-doped ZnO nanocones

Ni-doped ZnO flower-like nanocones with wurzite structures were produced by oxidative evaporation of Zn and Ni powders. The Ni doping did not change the ZnO wurtzite structure. Raman scattering indicated that the normal lattice vibration modes are related to the hexagonal ZnO. Ni clusters and Ni oxides phases did not existed in the sample as characterized by XRD, XPS, and TEM. Upon excitations the nanocones could emit strong green light at 525 nm, which can be directly observed with a digital camera. The magnetic measurement indicated that the Ni-doped ZnO nanocone was high-Curie-temperature magnetic semiconductor.     

Influence of CTAB surfactant on structural and optical properties of CuS and CdS nanoparticles by hydrothermal route

Metal sulphide CuS and CdS nanoparticles capped with Cetyltrimethylammonium bromide (CTAB) were synthesized by hydrothermal method. Structural, morphological, chemical composition, optical and luminescent properties were evaluated by different analytical techniques. X-ray diffraction (XRD) analysis of the CTAB capped metal sulfide nanoparticles reveals the formation of hexagonal structure. High-resolution transmission electron microscopy (HRTEM) images show that the morphology of the capped copper sulphide samples consists of hexagonal structure and capped cadmium has spherical shape and also confirms the crystalline nature of the particles with distinct lattice fringes. In FTIR spectroscopy, the composition of the CTAB capped CuS and CdS nanoparticles have been confirmed. The analysis of photoluminescence (PL) and optical transition show a red shift due to the reduction of band gap energy and it is attributed to the low defects and high crystallinity. The optical studies indicate that CuS and CdS nanoparticles with CTAB can be suitable for optoelectronic devices and photovoltaic applications.     

Synthesis,structural and optical characterization of Ni-doped ZnO nanoparticles

Nanocrystalline Zn_1−x Ni _x O (x = 0.00, 0.02, 0.04, 0.06, 0.08) powders were synthesized by a simple sol–gel autocombustion method using metal nitrates of zinc, nickel and glycine. Structural and optical properties of the Ni-doped ZnO samples annealed at 800 °C are characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive analysis using X-rays (EDAX), UV–visible spectroscopy and photoluminescence (PL). X-ray diffraction analysis reveals that the Ni-doped ZnO crystallizes in a hexagonal wurtzite structure and secondary phase (NiO) was observed with the sensitivity of XRD measurement with the increasing nickel concentration (x ≥ 0.04). The lattice constants of Ni-doped ZnO nanoparticles increase slightly when Ni²⁺ is doped into ZnO lattice. The optical absorption band edge of the nickel doped samples was observed above 387 nm (3.20 eV) along with well-defined absorbance peaks at around 439 (2.82 eV), 615(2.01 eV) and 655 nm (1.89 eV). PL measurements of Ni-doped samples illustrated the strong UV emission band at ~3.02 eV, weak blue emission bands at 2.82 and 2.75 eV, and a strong green emission band at 2.26 eV. The observed red shift in the band gap from UV–visible analysis and near band edge UV emission with Ni doping may be considered to be related to the incorporation of Ni ions into the Zn site of the ZnO lattice.     

Creation of Ferromagnetic Properties in Ni-Doped Na<Subscript>2</Subscript>WO<Subscript>4</Subscript>—Effect of Hydrogenation Post-treatment

Pure and Ni-doped sodium tungstate (Na₂WO₄) powders were synthesised by simultaneous crystallisation method. The effects of Ni doping on the structural, optical, and magnetic properties of the host Na₂WO₄ powder were studied. The study of X-ray diffraction shows that the incorporated Ni ions occupy locations in interstitial positions and substitution for W ion in the Na₂WO₃ lattice. A monophase cubic structure was obtained when the as-crystallised Na₂WO₄ powder was doped with Ni ions or annealed in hydrogen gas atmosphere (hydrogenation). The optical properties were studied by diffuse reflectance spectroscopy (DRS) technique. It was established that the direct bandgap of Na₂WO₄ exhibits red shift from 4.6 to 3.50 eV with Ni doping and blue shift to 5.13 eV with hydrogenation. The purpose of the present study is to study conditions necessary to prepare powders having room-temperature ferromagnetic (RT-FM) properties. Therefore, the Na₂WO₄ nano-powder was doped with Ni ions. RT-FM properties were obtained with Ni-doped Na₂WO₄ that was strongly enhanced by hydrogenation so that the energy product (EP) was increased by 213 %. This enhancement was attributed to the enhancement of the magnetic medium for the spin-spin (S-S) interaction inside the crystalline medium. In general, an experimental relationship was established between O vacancies, optical absorption, and magnetic properties of the studied crystal. Thus, it was proved, for the first time, the possibility of producing Na₂WO₄ having RT-FM, where magnetic characteristics can be tailored by doping and post-treatment under H₂ atmosphere, thus a new potential candidate to be used in magnetic applications of ferroelectric crystals.     

Study of high mobility carriers in Ni-doped CdO films

Cadmium oxide (CdO) doped with different amounts of nickel ion thin films have been prepared on silicon and glass substrates by vacuum evaporation technique. The effects of nickel doping on the structural, electrical, optical and optoelectronic properties of the host CdO films were systematically studied. The sample elemental composition was determined by the X-ray fluorescence spectroscopy method. The X-ray diffraction method was used to study the crystalline structure of the samples. It shows that some of Ni $^{3+}$ ions occupy mainly locations when in interstitial positions and Cd^2?+?-ion vacancies of CdO lattice. The bandgap of Ni-doped CdO suffers narrowing till 10–12% compared to undoped CdO. Such bandgap narrowing was studied within the framework of the available models. The electrical behaviours show that all the prepared Ni-doped CdO films are degenerate semiconductors. However, the nickel doping influences all the optoelectrical properties of CdO. Their d.c. conductivity, carrier concentration and mobility increased compared to undoped CdO film. The largest mobility of 112·6 cm²/V·s was measured for 1–2% Ni-doped CdO film. From optoelectronics point of view, Ni-doped CdO can be used in infrared-transparent-conducting-oxide (NIR–TCO) applications.