Sb Precursors Research Articles

Optical and electronic properties of high quality Sb-doped SnO2 thin films grown by mist chemical vapor deposition

Transparent Sb-doped epitaxial SnO2 (101) thin films were grown via mist chemical vapor deposition, a nonvacuum solution-based technique that involves the gas-assisted transport of ultrasonically-generated aerosols from simple aqueous Sn and Sb precursors. The electrical properties (at 300 K) of the resulting films could be varied from insulating to semimetallic via Sb doping, with a minimum resistivity of 8×10−4Ωcm, carrier concentrations up to 3.93×1020cm−3, and a maximum mobility of 48.1±0.1cm2V−1s−1, results similar to those achieved using molecular beam epitaxy and other more-sophisticated high vacuum techniques. Secondary ion mass spectrometry and Hall effect measurements revealed that 14% of Sb in the precursor solution incorporates into the Sb:SnO2 films, with almost all the Sb atoms forming shallow substitutional donors on the Sn-site. The increase in the carrier concentration with Sb doping produced a Burstein-Moss shift of the optical gap of 0.49 eV, without significantly reducing the more than 90% transparency of the films in the visible region. X-ray photoemission spectroscopy (hν=1486.6eV) showed an asymmetric Sn3d5/2 core-level emission characterized by a carrier concentration-dependent peak splitting. This effect was modeled in terms of the creation of an intrinsic plasmon loss satellite from which a conductivity effective electron mass of (0.49±0.11)me was determined.

The Enhanced Photovoltaic Performance of Sb2S3 Solar Cells by Thermal Decomposition of Antimony Ethyl Xanthate with Thiourea Doping

The thermal decomposition method is regarded as a simple and effective way to prepare Sb2S3 films. Herein, Sb2S3 films are prepared by thermal decompositions of antimony ethyl xanthate (Sb(xt)3). During the thermal decompositions process, sulfur vacancy defects are easily formed because of high temperatures. To reduce the sulfur vacancy defects in the final Sb2S3 films, thiourea (TU) is introduced in the Sb(xt) precursor. By doping with TU, the crystallinity of the Sb2S3 films improves and dense Sb2S3 films are formed. With the decrease in sulfur defects, the carrier concentrations are greatly increased from 2.5 × 1016 to 6.2 × 1016 cm−3. Compared with the no‐doping Sb2S3 solar cells, the power conversion efficiency of Sb2S3 solar cells with doping 25% TU is improved from 2.85% to 3.70%.

Plasma-assisted atomic layer deposition of germanium antimony tellurium compounds

Plasma atomic layer deposition of Ge-Sb-Te (GST) thin films using halogen-free precursors is reported. The Sb and Te precursors tris(aziridinyl)antimony (III) (Sb[cyclo-NC2H4]3) and di-n-butylditelluride [Te2(n-C4H9)2] were employed for the first time in the deposition of GST thin films. Conformal filling of trenches has been demonstrated. The film thickness ratio between the top and the wall/bottom of trenches was evaluated: for “wide” (7:1 aspect ratio) trenches—dbottom/dtop ≈ 0.65, and for “narrow” (23:1 aspect ratio) trenches dwall/dtop > 0.63. Due to the use of amino precursors the as-deposited GST films were doped with nitrogen.

Atomic Layer Deposition of GeTe and Ge–Sb–Te Films Using HGeCl3, Sb(OC2H5)3, and {(CH3)3Si}2Te and Their Reaction Mechanisms

In this paper, a new atomic layer deposition (ALD) process for depositing binary GeTe and ternary Ge–Sb–Te thin films is reported, where HGeCl3 and ((CH3)3Si)2Te were used as Ge and Te precursors, respectively. The precursors reacted together to form the films at a low substrate temperature of 50–100 °C, without involving any additional reactive process gas. HCl elimination from the Ge precursor to form the divalent Ge intermediate, GeCl2, is proposed to explain the formation of 1:1 composition stoichiometric GeTe films. The GeTe films are promising for use in phase change memory applications. Ternary Ge–Sb–Te films were deposited by combining the GeTe ALD process with a previously developed ALD process for Sb2Te3 films, where Sb(OC2H5)3 and ((CH3)3Si)2Te were employed respectively as the Sb and Te precursors. However, the composition of the ternary GeSbTe films deviated slightly from the desired GeTe–Sb2Te3 pseudobinary composition suggesting that a certain unwanted reaction was involved between the prev...

Shallow Heavily Doped n++ Germanium by Organo-Antimony Monolayer Doping.

Functionalization of Ge surfaces with the aim of incorporating specific dopant atoms to form high-quality junctions is of particular importance for the development of solid-state devices. In this study, we report the shallow doping of Ge wafers with a monolayer doping strategy that is based on the controlled grafting of Sb precursors and the subsequent diffusion of Sb into the wafer upon annealing. We also highlight the key role of citric acid in passivating the surface before its reaction with the Sb precursors and the benefit of a protective SiO2 overlayer that enables an efficient incorporation of Sb dopants with a concentration higher than 1020 cm-3. Microscopic four-point probe measurements and photoconductivity experiments show the full electrical activation of the Sb dopants, giving rise to the formation of an n++ Sb-doped layer and an enhanced local field-effect passivation at the surface of the Ge wafer.

Chemically Filled and Au-Coupled BiSbS3 Nanorod Heterostructures for Photoelectrocatalysis

The synergistic effects of foreign ion incorporation into a semiconductor host crystal lattice can produce new functional properties. This concept has been adopted in the design of various energy materials for light harvesting, charge transport, and energy storage applications. Going beyond the traditionally used group II–VI and III–V semiconductor nanostructures, herein, 1D materials involving Bi(III) and Sb(III) sulfides are reported. Upon Sb dilution into the Bi2S3 lattice, exciting new material properties, including induction of localized surface plasmon resonance (LSPR) and a drastic change to the 1D crystal growth pattern, were observed. The presence of the Sb(III) precursor along with Bi(III) led to nanotubes with controlled length as the ultimate product, and their transformation to nanorods via chemical filling emerged as a new fundamental mechanism of crystal growth. Due to its slow thermal decomposition rate, the Sb(III) precursor dominantly filled these tubes, resulting in graded alloy Bi1.09S...

Selective thin film synthesis of copper-antimony-sulfide using hybrid ink

In the copper-antimony-sulfide (Cu-Sb-S) system, four major phases (CuSbS2, Cu3SbS3, Cu3SbS4, Cu12Sb4S13) exist and are known to have good potentials as absorbers. To form thin films of Cu-Sb-S using a non-vacuum hybrid ink, Cu and Sb precursors were coated and sulfurized with a rapid thermal annealing (RTA) process. According to the ratio of Cu and Sb (Cu/Sb), different Cu-Sb-S thin films (CuSbS2 vs. Cu3SbS3, Cu3SbS4, Cu12Sb4S13) were easily obtained and confirmed by X-ray diffraction (XRD). However, although the Cu/Sb ratio of the hybrid ink was the same, different phases (Cu3SbS3, Cu3SbS4, Cu12Sb4S13) were observed depending on the reaction temperature, time, and pressure. It was shown that the reaction temperature, time, and pressure were also important factors for obtaining thin films. The sulfurized conditions to achieve thin films with a target phase were compared against different Cu/Sb ratios, reaction temperatures, reaction times, and chamber pressures.

Characterization of Cu-Based I-V-VI Thin Films Using Hybrid Inks

Cu(In,Ga)Se2 (CIGS) and Cu2ZnSnSe4 (CZTSe) have been studied as the most promising materials in solar cell research and production area. Until now, CIGS solar cell has already reported over 21 % conversion efficiency. Despite the real progress of efficiency, however, CIGS and CZTS absorbers in photovoltaic cells have been challenged by many problems, such as elemental scarcity, toxicity and structural complexity. Especially, complex stoichiometry and high process temperature are important obstacles to overcome because the elemental ratio of absorbers is hard to control and the bottom-cell can be easily degraded for fabricating high efficient tandem solar cell while the top-cell process is carrying on. Recently, Cu-based I-V-Vl materials, especially Cu-Sb-S phases, have been highlighted because of their characters, such as a band gap and a high optical absorption co-efficient. In the Cu-Sb-S phases, there are four major phases (CuSbS2, Cu3SbS3, Cu3SbS4, Cu12Sb4S13) but most of research have reported only about synthesis and characterization of nanocrystals. In this study, thin films of Cu-Sb-S phases were formed using non-vacuum process which is cost-effective. To form thin films of Cu-Sb-S using a non-vacuum hybrid ink, Cu and Sb precursors were coated and sulfurized with a rapid thermal annealing (RTA) process. However, each optimum sulfurization condition is needed to obtain single phase thin films of each material. The fabricating thin films were analyzed and confirmed as target phases. The characteristics of each Cu-Sb-S absorber and photovoltaic performances of fabricated cells will be presented.

Optimal biodiesel-additive synthesis under infrared excitation using pork bone supported-Sb catalyst: Engine performance and emission analyses

Glycerol (G) acetic acid (AA) esterification was conducted in an infrared irradiation (IRI) aided batch reactor for maximization of diacetin and triacetin yield (DT) using pork bone derived hydroxyapatite supported antimony (Sb) oxide catalyst. The catalyst possessed appreciable 40m2/g specific surface area; 4.5nm modal pore diameter and 0.0485cc/g pore volume with prominent Sb2O5 crystalline phase. Under derived optimal condition, 40% Sb precursor loading, 100°C reaction temperature and 6:1 AA:G mole ratio resulted maximum DT yield (88±1%). Notably, to achieve maximum DT yield (88±1%), conventionally heated batch reactor consumed 6 times more energy (reaction time 6h at 300J/s energy input rate) in comparison with IRI reactor (reaction time 2h at 150J/s energy input rate), indicating remarkable energy-efficiency of IRI. Additionally, synthesized product as additive to palm biodiesel evinced emission reduction by 50% and 20% for CO and HC respectively with 2 degrees depression in pour point.

Investigation on the atomic layer deposition of the Se doped Sb–Te phase change films using an alkyl-silyl precursor

We used TDMASb, Te(t-Bu)2, and Se(SiMe3)2 as precursors to investigate the behavior of atomic vapor deposition (AVD) during formation of Se doped Sb–Te phase change films. The deposition was prepared by a sequential recipe for the atomic layer deposition (ALD) reaction with consideration of the electrostatic interactions between the Se alkyl-silyl precursor and the Sb and Te precursors. The Sb–Te–Se ternary films could be deposited by AVD at temperatures of 80–300°C with fine controllability and high surface quality. The elemental composition of the films was controlled by varying the deposition temperature. The Se doping effect on the crystallization temperature and set resistance in the crystalline state was evaluated via electrical measurements and theoretical analyses by applying the glass transition temperature model and resonance bonding model. The results indicated that the incorporation of Se into Sb–Te films may provide for improved thermal stability and power consumption efficiency in phase-change random access memory (PCRAM) devices.

Reaction Mechanism Underlying Atomic Layer Deposition of Antimony Telluride Thin Films.

The mechanism underlying the deposition of SbTe films by alternating exposures to Sb(NMe2)3 and Te(GeMe3)2 was investigated. Sb(NMe2)3 and Te(GeMe3)2 were selected because they have very high vapor pressure and are free of Si, Cl, and O atoms in the molecules. The mechanism of deposition was proposed by density functional theory (DFT) calculation and was verified by in-situ quartz crystal microbalance (QCM) analysis. DFT calculation expected the ligand-exchange reactions between the Sb and Te precursors to form Me2NGeMe3 as the byproduct. QCM analysis indicated that a single -NMe2 group in Sb(NMe2)3 reacts with -TeGeMe3 on the surface to form an Sb2Te3 film, and that a small fraction of Sb is incorporated into the film by the thermal decomposition of Sb(NMe2)3. The Te(GeMe3)2 molecules were thermally stable up to 120 degrees C, while the Sb(NMe2)3 molecules decomposed at temperatures of 60 degrees C and higher. Sb-rich SbTe films with different Sb contents were prepared by controlling the partial decomposition of Sb(NMe2)3 molecules, which was enhanced by increasing the pulse time of the precursor.

Influence of Sb valency on the conductivity type of Sb-doped ZnO

Sb-doped ZnO thin films with different Sb concentrations were grown by varying mole ratio of Sb precursor to Zn precursor during the growth process using metal organic chemical vapor deposition technology. It was found that the valency of Sb changed from Sb3+ to Sb5+ in Sb doped ZnO with increasing mole ratio of Sb precursor to Zn precursor. The p-type ZnO was obtained only for ZnO films with lower mole ratio of Sb precursor. The conductivity type of Sb doped ZnO was changed from p-type to n-type accordingly. These results were suggested that the valency of Sb in ZnO is more important for obtaining p-type Sb doped ZnO thin films.

SnSb–TiC–C nanocomposite alloy anodes for lithium-ion batteries

SnSb–TiC–C nanocomposite alloy anodes for lithium-ion batteries have been synthesized by a mechanochemical process involving high-energy mechanical milling of Ti–Sn and Ti–Sb precursors with carbon black. Characterization of the formed nanocomposites using x-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) reveals that these alloys are composed of crystalline nanoparticles of SnSb dispersed in a matrix of crystalline TiC and amorphous carbon. The SnSb–TiC–C alloy shows an initial gravimetric capacity of 769 mAh g−1 (1385 mAh cm−3), an initial coulombic efficiency of 84.9%, and a tap density of 1.8 g cm−3. The buffer matrix of TiC and carbon in the nanocomposite alloy anodes accommodates the large volume change occurring during the charge–discharge process and leads to enhanced cyclability compared to pure SnSb anodes as well as previously published SnSb composites.

Chemical interaction and ligand exchange between a [(CH3)3Si]3Sb precursor and atomic layer deposited Sb2Te3films

The exchange reaction between the TMS group in [(CH3)3Si]3Sb and Sb2Te3film formed [(CH3)3Si]2Te, replacing Te in the film with Sb.

Ionic Liquid Electrochemical Synthesis of Earth Abundant Monophase Chalcostibite p-CuSbS2 Photo-absorber Thin films for Heterojunction Solar Cells With n-ZnO

ABSTRACTSingle step synthesis of monophase CuSbS2 thin films by electro-deposition in ionic liquid electrolyte based on choline chloride and urea (ChCl:U) eutectic mixture is described. The formation of binary CuxS and SbxSy film phases using CuCl2 and SbCl3 precursors along with Na2S2O3 as sulfur source in ChCl:U are established as -0.59 V and -0.36 V vs. Pt, respectively by cyclic voltammetry and used to optimize CuSbS2 thin films growth potential and precursor composition. CuSbS2 films deposited at -0.65 V vs Pt with 1:1 Cu to Sb precursor ratio at 80⁰C are highly crystalline in chalcostibite orthorhombic structure. Deviant Cu/Sb ratio at 1:0.71 and 1:1.4 reveal inclusion of Cu3SbS3 and Sb2S3, respectively. Direct 1.65 eV band gap for single phase CuSbS2 film and with inclusive secondary phases at 1.73±0.1 eV and 2.13 eV is observed. As-deposited CuSbS2 films are p-type and n-p hetero-junction device in the n-ZnO/p-CuSbS2/Ag structure shows rectifying I-V curves and dependence on the CuSbS2 film growth conditions.

Reason and Role of Atomic Layer Deposition for PCRAM and ReRAM Films

With a 13.4% CAGR, the demand for diverse memory applications in mobile phones, digital cameras, MP3 players, video game consoles and automobiles are exploding rapidly. To keep up with the diverse applications of memory devices, a number of next generation memory options are being studied, such as STTRAM, PCRAM and ReRAM. Most promising solutions for future non-volatile memories replacing conventional NAND are Phase Change Memory (PCRAM) and Resistive Memory (ReRAM). The growth of complex thin films through atomic layer deposition (ALD) is finding a broad range of applications for the production of next-generation memory devices. Conformal coating or gap-fill of high-quality thin films helps to mitigate multiple technology challenges encountered in new material development for high aspect ratio device structures. Similar step-coverage and composition controls are needed for fabricating next-generation non-volatile memory devices including phase-change memory (PCRAM) and resistive memory (ReRAM). This presentation will introduce a multi-wafers ALD system, QXP-8300 equipped with liquid injection vaporizers integrated with close-coupled showerhead in a small volume confined process space. This paper will also discuss recent new developments in equipment design to meet the technology needs as well as practical manufacturing targets (such as throughput and cost of ownership) in order to provide a production-worthy ALD solution. Applications in new memories such as PCRAM materials (such asGST), and O-vacancy controlled ReRAM materials will be reviewed. The formation of such engineered materials often requires chemical precursors that are low vapor-pressure liquids or even solids, posing a significant engineering challenge for production equipment design. With the help of thermal and flow modelling, designs are optimized for precursor evaporation, vapour delivery, and reactor geometry in order to maximize step-coverage and minimize ALD cycle time. Innovative platform architecture further improves system productivity, reduces defects, and enhances overall system cost of ownership. Results on both unit process and electrical characteristics will be presented for multiple ALD films generated from such a high-volume production system. Among the various candidate PCRAM alloys, GexSbyTez (GST) is the most promising because of its good scalability, low cost, and compatibility with conventional CMOS process. Conventional PCRAM had been researched and developed using physical vapour deposition. As devices scale down to 20 nm and beyond, confined and conformal GST film deposition into hole/trench structures is required, using ALD processes. However, to ensure good gapfill in a sub-20nm structures by ALD process, choice of precursors and precursors’ delivery challenges are far greater and require unique precursor delivery methodology to ensure good void-free gapfill while maintaining higher productivity. This paper highlights the progress made in ALD equipment development offering solutions for critical problems facing sub 20nm ALD PCRAM technology nodes. Using vaporizers suitable for Ge, Sb and Te precursors, ALD GST films were deposited in a Multi-wafer ALD system characterized by Small volume reactor and Closely coupled showerhead process. In this presentation, results are presented showing progress in GST film deposition into sub 20nm structures. ALD GST films were deposited under process conditions which achieved void-free gap-fill. By controlling injection dose and other parameters, such as temperature, pressure, etc., GST composition can be varied from Sb rich to Te rich in the films. Electrical characterization showing reset current <150uA due to confined cell enabled by ALD will be presented in this paper. Similarly, binary films of HfO2, HfO2/TiO2 and doped HfO2 deposited by ALD process showed lower forming voltage and high resistance ratio for ReRAM application. ALD can be used not only to tailor the composition of the films, it can also be utilized to conformally deposite multi-layers binary films for 3D ReRAM cross-point structure.

Properties of CuSbS2 thin films electrodeposited from ionic liquids as p-type absorber for photovoltaic solar cells

Electrodeposition of CuSbS2 semiconductor thin films for photovoltaic solar cells is investigated from ionic liquid electrolyte based on choline chloride–urea eutectic. Cyclic voltammetry study shows Cu and Sb deposition potential of −0.54V and −0.48V vs Pt, respectively. Highly crystalline CuSbS2 films in the chalcostibite orthorhombic structure without binary compound phases are electrodeposited at a potential of −0.65V vs Pt with Cu to Sb precursor ratio of 1:1 and Na2S2O3 as sulfur source in ionic liquid medium held at 80°C. Increase in Cu-precursor ratio (1:0.71) led to Cu3SbS3 ternary and that of Sb-precursor ratio (1:1.4) led to binary Sb2S3 phase inclusion in the phase field of the CuSbS2 films. Electrochemical impedance spectroscopy studies show diffusive ionic transport limited growth mechanism. Single phase CuSbS2 films show direct band gap energy of 1.66±0.01eV and films with inclusive secondary phases have band gap energy of 1.73±0.01eV. As-deposited CuSbS2 films are p-type and a hetero-junction in the nZnO–pCuSbS2 structure showed rectifying current–voltage behavior and low reverse current consistent with compact pinhole free CuSbS2 film synthesized by ionic liquid electrodeposition.

Colloidal synthesis of chalcostibite copper antimony sulfide nanocrystals

We report the colloidal synthesis of monodisperse phase pure chalcostibite CuSbS2 nanocrystals in high boiling point solvent. The use of dodecanethiol as ligands had an advantage over oleylamine on avoiding the hydrolysis of Sb precursor. The effect of reaction temperature and Cu/Sb feed molar ratio on the synthesis of copper antimony sulfide nanocrystals in dodecanethiol system was investigated. As a result of the reactivity difference between Cu and Sb precursors, the formation of CuSbS2 nanocrystals involves the preferential nucleation of Cu-rich nanocrystals and their subsequent reaction with remaining Sb precursors. The band gap of the resulting CuSbS2 nanocrystals was measured to be ~1.59eV.

Chalcogenisation of Cu–Sb metallic precursors into Cu3Sb(SexS1−x)3

Cu3SbS3 is a novel chalcogenide semiconductor with p-type conductivity and an energy bandgap of 1.84eV. By incorporating selenium into this material to form Cu3Sb(SexS1−x)3 where x=Se/(Se+S), the energy bandgap can be altered to be in the range 1.38–1.84eV for 0<x<0.49. The energy bandgap can hence be adjusted to be near the optimum for making the absorber layer for use in single and multi-junction photovoltaic solar cell devices. In this paper these materials were prepared using a two-stage process that involved magnetron sputtering of the Cu–Sb precursor layers followed by conversion to Cu3SbS3 by annealing in the presence of elemental sulphur and to Cu3Sb(SxSe1−x)3 by annealing in the presence of a mixture of sulphur and selenium. The films synthesised were characterised using scanning electron microscopy, energy dispersive x-ray analysis, x-ray diffraction, secondary ion mass spectroscopy and photo-electrochemical measurements. When the Cu3SbS3 was formed on glass substrates it had a cubic crystal structure whereas when it was formed on Mo-coated glass it had the monoclinic crystal structure. Likewise the layers of Cu3Sb(S,Se)3 formed on Mo-coated glass also had the monoclinic crystal structure. Spectral response curves were recorded over the spectral range 400–1400nm for semiconductor—electrolyte junctions. Photovoltaic solar cell devices were made using p-type Cu3Sb(SxSe1−x)3 as the absorber layer and n-type CdS as the buffer layer. The photovoltaic effect was observed in these devices.

Engineering the composition, morphology, and optical properties of InAsSb nanostructures via graded growth technique

Graded growth technique is utilized to realize the control over the composition, morphology, and optical properties of self-assembled InAsSb/InGaAs/InP nanostructures. By increasing the initial mole fraction of the Sb precursor during the graded growth of InAsSb, more Sb atoms can be incorporated into the InAsSb nanostructures despite the same Sb mole fraction averaged over the graded growth. This leads to a shape change from dots to dashes/wires for the InAsSb nanostructures. As a result of the composition and morphology change, photoluminescence from the InAsSb nanostructures shows different polarization and temperature characteristics. This work demonstrates a technologically important technique—graded growth, to control the growth and the resultant physical properties of self-assembled semiconductor nanostructures.