共掺杂n型CVD金刚石薄膜的结构和性能

利用微波等离子体化学气相沉积(MPCVD)技术制备硫掺杂及硼/硫共掺杂n型金刚石薄膜,探讨n型CVD金刚石薄膜的特性和共掺杂机理.研究结果显示:随着单一硫(S)掺杂含量的增加,金刚石薄膜导电激活能降低,薄膜生长速率减小,薄膜中非金刚石结构相增多;硼/硫(B-S)共掺杂有利于增加硫在金刚石中的固溶度,提高硫在金刚石晶体中的掺杂率,降低金刚石薄膜的导电激活能(在0.26～0.33eV);与单一S掺杂相比较,B-S共掺杂金刚石薄膜生长速率低,薄膜质量和晶格完整性好;霍耳效应测试表明硫掺杂和硼/硫共掺杂金刚石薄膜具有n型导电特征,载流子浓度在1016-1018/cm3之间,载流子迁移率在7～80cm2V-1s-1之间.采用B-S共掺杂技术有利于提高CVD金刚石薄膜的晶格完整性,使得B-S共掺杂金刚石薄膜具有更高的载流子迁移率.     

磁控溅射制备Nb掺杂IZO薄膜光电学性能研究

通过磁控溅射方法制备一种新型薄膜晶体管有源层材料Nb掺杂的氧化铟锌(IZO)非晶薄膜(a-INZO)。运用XRD、光致发光、Hall测试等检测方法分析INZO薄膜微观结构、缺陷状态以及电学性能。光致发光结果表明,INZO相较于Ga掺杂的IZO(IGZO)具有更低的深能级缺陷密度。Hall效应测试结果表明,通过调节溅射过程中氧气流量可有效控制INZO薄膜载流子浓度,使之适合于制备薄膜晶体管(TFT)器件。INZO薄膜迁移率随载流子浓度的变化规律符合渗流传导模型,载流子浓度较低时,迁移率随载流子浓度增加而增加;载流子浓度较高时,迁移率下降,光学数据的分析表明其带尾态宽度较大,结构更无序。提高溅射基底温度可有效提高迁移率,但对薄膜无序度的改善并不明显。     

近距离升华制备CdTe掺Te薄膜的结构与电性能研究

采用近距离升华(Close-Spaced-Sublimation,CSS)技术制备CdTe及掺Te薄膜.并利用XRF、XRD、SEM及Hall系统研究了其含量、结构、表面形貌和电性能.结果表明,CSS技术制备的CdTe薄膜晶形好,晶粒度较RF方法制备的薄膜增大约100倍.Te掺入CdTe薄膜后,改变了CdTe膜的结晶特性,适当掺入Te可以促进CdTe晶格的生长,并导致Cdrre膜晶格常数变大.薄膜面电阻率降低,面载流子浓度增大,以及载流子迁移率的增大,表明掺杂Te后CdTe膜的电导性能大大改善.     

硼掺杂对直流热阴极CVD金刚石薄膜生长特性的影响

采用直流热阴极CVD法以B(OCH3)3为掺杂剂制备了硼掺杂金刚石薄膜,利用等离子体发射光谱、SEM、Raman和XRD研究了硼掺杂对金刚石薄膜生长特性的影响,通过与未掺杂金刚石薄膜的对比发现:在直流热阴极CVD系统中,低浓度硼掺杂条件下能够长时间维持稳定的辉光放电. 掺硼后辉光等离子体活性基团(Hα、Hβ、C2、CH)的种类没有改变,但C2基团的浓度升高,而CH基团的浓度下降,薄膜的生长速率提高到0.65mg·cm-2·h-1. 硼掺杂金刚石薄膜为多晶薄膜,晶体生长良好,取向以(111)晶面为主,质量较未掺杂薄膜有所提高. 硼原子以取代或填隙的方式掺杂进入金刚石晶格,没有破坏金刚石晶体结构.     

离子注入法制备N掺杂p型ZnO薄膜

采用离子注入技术对射频磁控溅射制备的ZnO薄膜进行N掺杂,通过退火实现了ZnO薄膜的p型转变.利用X射线衍射(XRD)和Hall实验对样品热退火前后的性能进行了研究.实验数据表明,该掺杂方法能得到稳定的p型ZnO薄膜,其电学性能随热退火温度的升高和时间的延长而进一步改善,其中在950℃、7min退火条件时,载流子浓度为1.68E 16cm-3,电阻率为41.5Ω·cm.     

大尺寸掺硼宝石级金刚石单晶的高温高压合成及电学性质研究

在5.4GPa、1200～1400℃条件下,进行掺硼金刚石单晶的合成研究。成功合成出了重0.2g,径向尺寸达6.0mm的优质掺硼金刚石单晶。考察了合成体系中硼添加量对晶体透光度的影响。利用伏安特性和霍尔测试,得到了掺硼金刚石单晶常温电阻率、霍尔系数及霍尔迁移率和合成体系中硼添加量的关系。研究发现,随着合成体系中硼添加量的增加,晶体的电阻率和霍尔迁移率都呈下降趋势;霍尔系数随硼添加量的增加先下降后上升。随着硼添加量的增加:晶体常温电阻率下降,表明硼杂质已进入到金刚石晶体中。霍尔迁移率的下降,可能是晶体缺陷增多对载流子散射所致。霍尔系数先减小后增大,这可能与进入金刚石的硼元素量增大及晶体缺陷增多有关。     

共掺浓度对Na-Al共掺杂ZnO薄膜微观结构和光电性能的影响

在石英玻璃衬底上,通过溶胶-凝胶旋涂法制备得到钠铝(Na-Al)共掺氧化锌(ZnO)薄膜(NAZO)。研究不同NaAl共掺杂浓度对ZnO薄膜的结晶性、微观结构、光电性能的影响。结果表明:所有NAZO薄膜样品都沿c轴择优取向生长;适当的Na-Al共掺浓度,可以提高ZnO薄膜结晶性,提高薄膜的载流子迁移率;同时还可以观察到NAZO薄膜表面生长出六角柱状结构晶粒。随着Na-Al元素掺杂浓度的改变,所获薄膜的最高平均光学透过率达到95%。由于元素间固溶比的不同,适当的浓度可以提高Na-Al元素的掺杂效率和薄膜内部的载流子浓度,降低薄膜电阻率,NAZO薄膜最低电阻率为4.7×10-2Ω·cm。     

Fe3+离子敏感Ge-Sb-Se-Fe(Ni)系薄膜的掺杂行为研究

本文用电子束蒸发方法制备了掺Fe、Ni的Ge-Sb-Se-Fe(Ni)薄膜.Hall效应测得薄膜均为p型半导体.对薄膜的研究表明Ge-Sb-Se中不同过渡金属元素掺杂因失电子能力差异而形成了不同的网络结构,高电负性过渡金属元素掺杂倾向于形成较少缺陷态的网络结构;Al的热扩散共掺杂使载流子浓度提高,且其浓度的提高可以抵消杂质散射引起的迁移率下降,降低薄膜的方块电阻.     

掺硼金刚石膜的制备及其应用

金刚石虽然具有极为优异的性能,如具有很大的能隙,高的电子迁移率、空穴迁移率和高热导率,以及负的电子亲和势,但要将它用于半导体材料时还不能直接使用,必须要先进行金刚石的P型和n型掺杂。因此,研究金刚石的P型和n型掺杂具有很重要的现实意义。在金刚石薄膜中掺杂时,一般是掺入硼原子以实现P型掺杂,掺入氮原子或磷原子以实现n型掺杂。然而,由于N和P在金刚石中的施主能级太深,现在n型掺杂金刚石薄膜制备尚不成功,这是金刚石实用化的障碍。本文介绍了金刚石膜掺硼目的、方法和制备,总结了掺硼金刚石膜在微电子、电化学、光电子、工具等领域应用状况以及存在问题。     

溶胶-凝胶法制备AZO薄膜及Al掺杂机理的研究

采用溶胶-凝胶法和浸渍提拉法成功制备了Al掺杂ZnO薄膜(以下简称AZO薄膜)。用X射线衍射仪(XRD)、场发射扫描电镜(FE-SEM)、分光光度计、霍尔(Hall)测量仪,分别研究了不同Al的掺杂浓度对薄膜的结晶性能、微观形貌和光电性能的影响,探讨了Al的掺杂机理。结果表明,Al的掺杂存在最佳值,当Al掺杂摩尔浓度为5%时,AZO薄膜的结晶性能、微观形貌和光电性能最佳,其透光率在80%以上,电阻率为2.1×102Ω·cm,霍尔迁移率为0.23cm2/V·s,载流子浓度为7.81×1014cm-3。     

Dodecaborane‐Based Dopants Designed to Shield Anion Electrostatics Lead to Increased Carrier Mobility in a Doped Conjugated Polymer

One of the most effective ways to tune the electronic properties of conjugated polymers is to dope them with small‐molecule oxidizing agents, creating holes on the polymer and molecular anions. Undesirably, strong electrostatic attraction from the anions of most dopants localizes the holes created on the polymer, reducing their mobility. Here, a new strategy utilizing a substituted boron cluster as a molecular dopant for conjugated polymers is employed. By designing the cluster to have a high redox potential and steric protection of the core‐localized electron density, highly delocalized polarons with mobilities equivalent to films doped with no anions present are obtained. AC Hall effect measurements show that P3HT films doped with these boron clusters have conductivities and polaron mobilities roughly an order of magnitude higher than films doped with F₄TCNQ, even though the boron‐cluster‐doped films have poor crystallinity. Moreover, the number of free carriers approximately matches the number of boron clusters, yielding a doping efficiency of ≈100%. These results suggest that shielding the polaron from the anion is a critically important aspect for producing high carrier mobility, and that the high polymer crystallinity required with dopants such as F₄TCNQ is primarily to keep the counterions far from the polymer backbone.     

A comparative study of p-type diamond films using Raman and transport measurements

The influence of deposition temperature in the properties of synthetic diamond films grown by two different chemical vapor deposition (CVD) techniques, hot-filament- and microwave-plasma-assisted, was investigated. These samples were obtained using the optimal growth conditions previously achieved in this work. Raman spectroscopy was employed in order to investigate the diamond film quality as a function of the deposition temperature. It was found that the nondiamond carbon bands decrease as the deposition temperature increases for both the deposition methods, leading to higher-quality diamond films. The micro- and macro-Raman spectra showed that the nondiamond band is already present in a single diamond grain. Both techniques provided well homogeneous diamond films and with equivalently good quality. Boron-doped diamond films with different carrier concentration levels were also studied. In order to get details about the electrical properties of the films, resistivity as a function of the boron concentration—in association with Raman spectra—and temperature-dependent transport measurements were employed. The results showed that the boron doping is the main responsible for the conductivity and that the variable range hopping (VRH) mechanism dominates the transport in these doped diamond films.     

Effect of the substrate temperature on the structural, optical and electrical properties of spray-deposited CdS:B films

Boron doped CdS films have been deposited by spray pyrolysis method onto glass substrate temperature in the range of 350–450 °C. And the effect of substrate temperature (T _s) on the structural, electrical and optical properties of the films were studied. The structural properties of boron doped CdS films have been investigated by (XRD) X-ray diffraction techniques. The X-ray diffraction spectra showed that boron doped CdS films are polycrystalline and have a hexagonal (wurtzite) structure. By using SEM analysis, the surface morphology of the films was observed as an effect of the variation of substrate temperature. The substrate temperature is directly related with the shift detected in the band gap values derived from optical of parameters and the direct band gap values were found to be in the region of 2.08–2.44 eV. The electrical studies showed that the film deposited at the substrate temperature 400 °C had high carrier concentration and Hall mobility and minimum resistivity. This resistivity value decreased with increase in temperature up to 400 °C indicating the semiconducting nature of B- doped CdS films. The lattice parameter, grain size, microstrain and dislocation densities were calculated and correlated with the substrate temperature (T _s ).     

A comparison between ZnO films doped with 3d and 4f magnetic ions

We present electrical and magnetic properties of ZnO films doped with 3d (Mn) and 4f (Gd or Nd) magnetic ions grown on a-plane Al₂O₃ substrates. Both for films doped with 3d magnetic ions and for films doped with 4f magnetic ions, Hall investigations revealed that the carrier concentration decreases and the resistivity increases with increasing the oxygen partial pressure during the pulsed laser deposition growth, probably because the formation of oxygen vacancies is hindered. Measurements of magnetic properties revealed ferromagnetism above room temperature with magnetic moments up to 0.2 μ_B/Mn ion in insulating ZnO:Mn films co-doped with 0.1% P and up to 0.3 μ_B/Gd ion in n-conducting ZnO:Gd films co-doped with 0.2% Al.     

Effects of growth ambient on electrical properties of Al-N co-doped p-type ZnO films

p-Type zinc oxide thin films with c-axis orientation were prepared in N₂O-O₂ atmosphere by an Al-N co-doping method using reactive magnetron sputtering. Secondary ion mass spectroscopy (SIMS) measurements indicate that as-grown ZnO films were co-doped with Al and N. Hall effect measurements show a dependence of types of conduction, carrier concentration and mobility of as-grown ZnO films on N₂O partial pressure ratios. p-Type ZnO thin films deposited in a N₂O partial ratio of 10% show the highest hole concentration of 1.1×10¹⁷ cm⁻³, the lowest resistivity of about 100 Ω cm, and a low mobility of 0.3 cm² V⁻¹ s⁻¹.     

Transport properties of thin SnO2〈Sb〉 films grown by pulsed laser deposition

Thin SnO₂<Sb> films grown by pulsed laser deposition have been characterized by X-ray diffraction, optical spectroscopy, and scanning electron microscopy. The carrier mobility and concentration in the films have been determined as functions of target composition (0–8 at % Sb) using Hall effect measurements, and the resistivity of the films has been measured by a four-probe technique. The lowest resistivity (ρ = 2 × 10^?3 Ω cm) and the highest transmission (? 85%) of the films in the spectral range 400-800 nm have been obtained at a target composition Sb/(Sn + Sb) = 2 at %. The observed variation in the resistivity of the films is determined by changes in carrier concentration to a greater extent than by changes in carrier mobility. X-ray photoelectron spectroscopy results demonstrate that the predominant charge state of the antimony in the films is Sb⁵⁺.     

Properties of ZnO thin films co-doped with hydrogen and fluorine

ZnO films co-doped with fluorine and hydrogen were prepared on Corning glass by radio frequency magnetron sputtering of ZnO targets with varying amounts of ZnF2 in H2/Ar gas mixtures of varying H2 content. The ZnO films' electrical, optical, and structural properties in combination with their compositional properties were investigated. A small addition of H2 to the sputtering gas caused a drastic increase of Hall mobility with a marginal increase in carrier concentration, indicating an effective passivation of grain boundaries due to hydrogenation. For further increase of H2 in sputter gas, the Hall mobility remained at a relatively constant level while the carrier concentration increased steadily. Most of the ZnO films co-doped with fluorine and hydrogen showed average transmittance higher than 83% in the 400-800 nm range, while the average absorption coefficients were lower than 600 cm(-1), implying very low absorption loss in these films. It was discovered that the fabrication of ZnO films with a Hall mobility higher than 40 cm2/Vs and a very low absorption loss in the visible range is possible by co-doping hydrogen and fluorine.     

Thickness dependence of the electrical and structural properties of In2O3:Sn films

Films of In₂O₃:Sn (10 wt.% Sn) of various thicknesses were deposited onto heated glass substrates (450 °C) by spray pyrolysis. The electrical and structural properties were studied for different thicknesses, and the scattering mechanism is discussed. Hall measurements showed that thicker films (about 500 mm) have relatively higher Hall mobilities compared with those of thinner films. The electrical resistivity of a film about 600 nm thick was found to be about 2.66 x 10^-6 ωm at room temperature, and the average transmission in the visible range was found to be 86%. The high carrier concentration (6.49 × 10²⁶ m^-3) and the negligible dependence of the electrical properties on temperature show that the films are degenerate. The relationship between carrier concentration and Hall mobility revealed that the ionized impurity scattering centres were the dominant cause of scattering.