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A comparison of the morphological and electrical properties of sol-gel dip coating and atomic layer deposition of ZnO on 3D nanospring mats
摘要： We report on the morphological and electrical properties, with (light) and without (dark) UV illumination, of conformal coatings of ZnO on silica nanosprings deposited by sol-gel and atomic layer deposition (ALD) for the first time. Field Emission Scanning Electron Microscopy (FESEM) imaging showed that both methods produce conformal coatings of ZnO on the nanosprings. The surface of the sol-gel coatings exhibited cracks at higher numbers of dipping/sintering cycles, while the morphology of ALD ZnO films were always smooth and devoid of cracks. The effective photoconductivity of the sol-gel ZnO coated nanospring mats increased nonlinearly with increasing coating thickness. The corresponding dark effective conductivity of the sol-gel ZnO coated nanospring mats also increased within the same thickness range. Alternatively, the effective photoconductivity of the ALD ZnO coated nanospring mats increased linearly with increasing coating thickness. The corresponding dark effective conductivity also increased within the same thickness range. The superior effective conductivity and photoconductivity of the ALD ZnO coated nanospring mats is attributed to the uniformity of the coating and the absence of cracks, which are observed for the thicker sol-gel ZnO coatings.
关键词： atomic layer deposition (ALD),semiconductors,sol-gel,nanosprings,field emission scanning electron microscopy,conductivity,ZnO
更新于2025-09-23 15:22:29
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Energetic Ions during Plasma-Enhanced Atomic Layer Deposition and their Role in Tailoring Material Properties
摘要： Plasma-enhanced atomic layer deposition (PEALD) has obtained a prominent position in the synthesis of nanoscale films with precise growth control. Apart from the well-established contribution of highly reactive neutral radicals towards film growth in PEALD, the ions generated during plasma exposure can also play a significant role. In this work, we report on the measurements of ion energy and flux characteristics on grounded and biased substrates during plasma exposure to typically used for PEALD (O2, H2, N2) were measured in a commercial 200-mm remote inductively coupled plasma ALD system equipped with RF substrate biasing. IFEDFs were obtained using a gridded retarding field energy analyzer and the effect of varying ICP power, pressure and bias conditions on the ion energy and flux characteristics of the three reactive plasmas were investigated. The properties of three material examples – TiOx, HfNx and SiNx – deposited using these plasmas were investigated on the basis of the energy and flux parameters derived from IFEDFs. Material properties were analyzed in terms of the total ion energy dose delivered to a growing film in every ALD cycle, which is a product of the mean ion energy, total ion flux and plasma exposure time. The properties responded differently to the ion energy dose depending on whether it was controlled with RF substrate biasing where ion energy was enhanced, or without any biasing where plasma exposure time was increased. This indicated that material properties were influenced by whether or not ion energies exceeded energy barriers related to physical atom displacement or activation of ion-induced chemical reactions during PEALD. Furthermore, once ion energies were enhanced beyond these threshold barriers with RF substrate biasing, material properties became a function of both the enhanced ion energy and the duration for which the ion energy was enhanced during plasma exposure. These results have led to a better insight into the relation between energetic ions and the ensuing material properties, e.g., by providing energy maps of material properties in terms of the ion energy dose during PEALD. It serves to demonstrate how the measurement and control of ion energy and flux characteristics during PEALD can provide a platform for synthesizing nanoscale films with the desired material properties.
关键词： ion energy dose,ion energy flux,ion bombardment,atomic layer deposition,RFEA,thin film,substrate biasing,ion flux,ion energy control,retarding field energy analyzer,plasma ALD
更新于2025-09-23 15:21:21
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Design and Operation of an Optically-Accessible Modular Reactor for Diagnostics of Thermal Thin Film Deposition Processes
摘要： The design and operation of a simple, optically-accessible modular reactor for probing thermal thin film deposition processes, such as atomic layer deposition processes (ALD) and chemical vapor deposition (CVD), is described. This reactor has a nominal footprint of 225 cm2 and a mass of approximately 6.6 kg, making it small enough to conveniently function as a modular component of an optical train. The design is simple, making fabrication straightforward and relatively inexpensive. Reactor operation is characterized using two infrared absorption measurements to determine exhaust times for tetrakis(dimethylamino)titanium and water, proto-typical ALD precursors, in a pressure and flow regime commonly used for ALD.
关键词： ALD,atomic layer deposition,in situ,reactor,diagnostics,chemical vapor deposition,CVD,optical cell
更新于2025-09-23 15:21:21
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Optical properties of ZnO deposited by atomic layer deposition (ALD) on Si nanowires
摘要： In this work, we report proof-of-concept results on the synthesis of Si core/ ZnO shell nanowires (SiNWs/ZnO) by combining nanosphere lithography (NSL), metal assisted chemical etching (MACE) and atomic layer deposition (ALD). The structural properties of the SiNWs/ZnO nanostructures prepared were investigated by X-ray diffraction, Raman spectroscopy, scanning and transmission electron microscopies. The X-ray diffraction analysis revealed that all samples have a hexagonal wurtzite structure. The grain sizes are found to be in the range of 7–14 nm. The optical properties of the samples were investigated using reflectance and photoluminescence spectroscopy. The study of photoluminescence (PL) spectra of SiNWs/ZnO samples showed the domination of defect emission bands, pointing to deviations of the stoichiometry of the prepared 3D ZnO nanostructures. Reduction of the PL intensity of the SiNWs/ZnO with the increase of SiNWs etching time was observed, depicting an advanced light scattering with the increase of the nanowire length. These results open up new prospects for the design of electronic and sensing devices.
关键词： nanosphere lithography (NSL),atomic layer deposition (ALD),Silicon nanowires (SiNWs),metal-assisted chemical etching (MACE),ZnO
更新于2025-09-23 15:21:21
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Investigation of the Physical Properties of Plasma Enhanced Atomic Layer Deposited Silicon Nitride as Etch Stopper
摘要： Correlations between physical properties linking film quality with wet etch rate (WER), one of the leading figures of merit, in plasma-enhanced atomic layer deposition (PEALD) grown silicon nitride (SiNx) films remain largely unresearched. Achieving a low WER of a SiNx film is especially significant in its use as an etch stopper for technology beyond 7 nm node semiconductor processing. Herein, we explore the correlation between the hydrogen concentration, hydrogen bonding states, bulk film density, residual impurity concentration, and the WERs of PEALD SiNx using Fourier transform infrared spectrometry, X-ray reflectivity, and spectroscopic ellipsometry, etc. PEALD SiNx films for this study were deposited using hexachlorodisilane and hollow cathode plasma source under a range of process temperatures (270 °C – 360 °C) and plasma gas compositions (N2/NH3 or Ar/NH3) to understand the influence of hydrogen concentration, hydrogen bonding states, bulk film density, and residual impurity concentration on the WER. Varying hydrogen concentration and differences in the hydrogen bonding states resulted in different bulk film densities, and accordingly, a variation in WER. We observe a linear relationship between hydrogen bonding concentration and WER as well as a reciprocal relationship between bulk film density and WER. Analogous to the PECVD SiNx processes, a reduction in hydrogen bonding concentration arises from either (1) thermal activation or (2) plasma excited species. However, unlike the case with silane (SiH4)-based PECVD SiNx, PEALD SiNx WERs are affected by residual impurities of Si precursors (i.e., chlorine impurity). Thus, possible wet etching mechanisms in HF in which the WER is affected by hydrogen bonding states or residual impurities are proposed. The shifts of amine basicity in SiNx due to different hydrogen bonding states and the changes in Si electrophilicity due to Cl impurity content are suggested as the main mechanisms that influence WER in the PEALD processes.
关键词： plasma-enhanced ALD (PEALD),bulk film density,hexachlorodisilane (HCDS),wet etch rate (WER),silicon nitride,hydrogen/chlorine content,atomic layer deposition (ALD),hydrogen bonding state
更新于2025-09-23 15:21:01
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Channel-Length Dependent Performance Degradation of Thermally Stressed IGZO TFTs
摘要： The focus of this work is on the performance degradation of thermally stressed IGZO TFTs with SiO2 for both the gate dielectric and back-channel passivation material. I-V characteristics of TFTs with bottom-gate (BG) and double-gate (DG) electrode configurations were observed to left-shift and degrade with thermal stress. Experimental results indicate the instability occurs either directly or indirectly due to the influence of H2O within the passivation oxide above the IGZO channel region. An atomic layer deposition (ALD) alumina capping layer applied immediately following the passivation oxide anneal was successful in improving thermal stability. Channel length dependence was observed where longer channel DG devices were more prone to degradation. A hypothesis has been developed with H2O as the expected origin of this phenomenon. Experiments have been specifically designed to establish the feasibility of the proposed mechanism. Furthermore, DG devices which exhibit enhanced thermal stability are presented.
关键词： thermal stability,SiO2 passivation,ALD alumina capping,IGZO TFTs,channel length dependence
更新于2025-09-23 15:21:01
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Combustion-processed NiO/ALD TiO2 bilayer as a novel low-temperature electron transporting material for efficient all-inorganic CsPbIBr2 solar cell
摘要： Low-temperature ALD TiO2 electron transporting layers (ETLs) are promising for all-inorganic perovskite solar cells (PSCs), such as the CsPbIBr2-based ones. However, the non-ideal interfacial level-alignment between ALD TiO2 and CsPbIBr2, as well as the concomitant defects in ALD TiO2 during preparation of upper CsPbIBr2 film severely limit the performance of final PSC. We report herein a new design of ETL by combining ALD TiO2 with low-temperature combustion-processed NiO. Although the underlying NiO layer has a p-type conductivity and is known as a hole transporting layer (HTL), the NiO/ALD TiO2 bilayer can serve as an ETL with fewer traps, larger conduction band minimum (CBM) offset with CsPbIBr2 film, along with the similar optical transmittance, in contrast with individual ALD TiO2 ETL. Consequently, the resulting optimized CsPbIBr2 PSC yields the superior efficiency of 9.71% and photovoltage of 1.272 V, both of which exceed those of the one based on individual ALD TiO2 ETL and even so-gel TiO2 ETL. Our work verifies the great applicability of NiO/ALD TiO2 ETL for CsPbIBr2 PSC and thereby explores a promising way to develop more low-temperature ETLs by combining conventional HTLs with ALD TiO2 layers.
关键词： NiO/TiO2 bilayer,ALD,Low temperature,All-inorganic CsPbIBr2 solar cells,Solution combustion,Electron transporting material
更新于2025-09-23 15:19:57
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Duala??shelled RbLi(Li3SiO4)2:Eu2+@Al2O3@ODTMS phosphor as a stable green emitter for higha??power LED Backlights
摘要： The stability of luminescent materials is a key factor for the practical application in white light-emitting diodes (LEDs). Poor chemical stability of narrow-band green-emitting RbLi(Li3SiO4)2:Eu2+ (RLSO:Eu2+) phosphor hinders its further commercialization even if it possesses excellent stability against thermal quenching. Herein, we propose an efficient protection scheme by combining the surface coating of amorphous Al2O3 and hydrophobic modification by octadecyltrimethoxysilane (ODTMS) to construct the moisture-resistant dual-shelled RLSO:Eu2+@Al2O3@ODTMS composite. The growth mechanisms of both Al2O3 inorganic layer and silane organic layer on the phosphor surface are investigated, which can remarkably improve the water-stability of this narrow-band green emitter. The evaluation result of the white LED by employing this composite as green component demonstrates that RLSO:Eu2+@Al2O3@ODTMS is a promising candidate for the high-performance display backlights, and this dual-shelled strategy provides an alternative method to improve the moisture-resistant property of humidity-sensitive phosphors.
关键词： ALD,dual-shelled,hydrophobic,LED backlights,phosphors
更新于2025-09-23 15:19:57
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Duala??shelled RbLi(Li3SiO4)2:Eu2+@Al2O3@ODTMS phosphor as a stable green emitter for higha??power LED Backlights
摘要： The stability of luminescent materials is a key factor for the practical application in white light-emitting diodes (LEDs). Poor chemical stability of narrow-band green-emitting RbLi(Li3SiO4)2:Eu2+ (RLSO:Eu2+) phosphor hinders its further commercialization even if it possesses excellent stability against thermal quenching. Herein, we propose an efficient protection scheme by combining the surface coating of amorphous Al2O3 and hydrophobic modification by octadecyltrimethoxysilane (ODTMS) to construct the moisture-resistant dual-shelled RLSO:Eu2+@Al2O3@ODTMS composite. The growth mechanisms of both Al2O3 inorganic layer and silane organic layer on the phosphor surface are investigated, which can remarkably improve the water-stability of this narrow-band green emitter. The evaluation result of the white LED by employing this composite as green component demonstrates that RLSO:Eu2+@Al2O3@ODTMS is a promising candidate for the high-performance display backlights, and this dual-shelled strategy provides an alternative method to improve the moisture-resistant property of humidity-sensitive phosphors.
关键词： ALD,dual-shelled,hydrophobic,LED backlights,phosphors
更新于2025-09-23 15:19:57
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Unipolar N-type Conduction in Black Phosphorus Induced by Atomic Layer Deposited MgO
摘要： Two-dimensional (2D) black phosphorus (BP) holds great promise for future nanoscale field-effect-transistors owing to its finite band gap and expected high carrier mobility. Nevertheless, while most studies have reported unipolar p-type or ambipolar BP transistors with a hole conduction dominance, excellent n-type transport in BP has been a critical challenge. Here, we report unipolar n-type BP transistors realized by an MgO capping layer via atomic layer deposition. By coverage with 20-nm-thick MgO, remarkable electron conduction is obtained in transistors fabricated on BP flakes of thicknesses from 2.6 to 7.6 nm, accompanied by fully suppressed hole transport. Furthermore, the unipolar electron transport is found to retain (or even improve) after a period of 6 months, with the highest extrinsic electron mobility reaching 135.9 cm2/Vs. The effective approach to realizing unipolar n-FETs of BP demonstrated in this work paves the way to the implementation of BP-based CMOS digital logic circuits.
关键词： MgO,Black phosphorus,n-type conduction,ALD,Transistors
更新于2025-09-19 17:15:36