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Bi-layer high-<i>k</i> dielectrics of Al<sub>2</sub>O<sub>3</sub>/ZrO<sub>2</sub> to reduce damage to MoS<sub>2</sub> channel layers during atomic layer deposition
摘要： To implement Two-dimensional (2D) transition metal dichalcogenides (TMDCs) in electric devices, a top-gated device structure is desired. However, there has been possibility of the channel layer being damaged during the upper dielectric deposition process. Because several layers of 2D TMDCs are atomically thin, the damage may significantly degrade the overall electrical performance. In this study, we investigated the damage to molybdenum disulfide (MoS2) during the atomic layer deposition (ALD) of single dielectrics of Al2O3 and ZrO2. We observed the MoS2 layers were damaged, depending on the ALD process conditions; the kind of oxidant and the growth temperature. To reduce the damage, we formed a bi-layered Al2O3/ZrO2 dielectric structure by developing a two-step ALD process. It is notable that the electrical performance of the device was significantly improved compared to those using the single dielectrics, indicating this two-step process is a promising candidate to satisfy the requirements of future 2D TMDCs-based electronics.
关键词： 2D TMDC,high-k dielectric,Atomic layer deposition,MoS2
更新于2025-09-10 09:29:36
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Construction of heterojunction photoelectrode via atomic layer deposition of Fe2O3 on Bi2WO6 for highly efficient photoelectrochemical sensing and degradation of tetracycline
摘要： The present paper describes the fabrication of a heterojunction photoelectrode by combining the wet chemical synthesis of Bi2WO6 with the formation of Fe2O3 layer by atomic layer deposition (ALD) technique. Fe2O3 with different atomic thicknesses was layered onto spin-coated Bi2WO6 nanoflakes by controlling the number of deposition cycles. The influence of the thickness of the Fe2O3 layers on photoelectrocatalytic detection and remediation was also studied. The deposition of a 15-nm layer of Fe2O3 on Bi2WO6 led to the best photoelectrochemical response under visible light activation. The performance of 15-nm Fe2O3–Bi2WO6 (4.3 μA/cm2) was 3.6 times higher than that of pristine Bi2WO6 (1.2 μA/cm2) at an external bias of 0.6 V. The enhanced performance was due to the increased spectral breadth of light absorption and efficient transfer of photogenerated charge carriers by the suppression of electron–hole pairs. The optimized photoelectrode detected tetracycline antibiotic in aqueous solution with a 0.3 μM limit of detection and photoelectrocatalytically degraded around 95% tetracycline. The heterojunction photoelectrode structure prepared using ALD enables inexpensive, non-enzymatic, amperometric determination and degradation of tetracycline in a stable and reproducible manner via a deduced mechanism. Our strategy can be used to fabricate photoelectrodes for a wide range of applications.
关键词： Atomic layer deposition,Sensing,Heterojunction photoelectrode,Photoelectrochemical,Fe2O3-Bi2WO6
更新于2025-09-10 09:29:36
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Oxidation-Induced Changes in the ALD-Al2O3/InAs(100) Interface and Control of the Changes for Device Processing
摘要： InAs crystals are emerging materials for various devices like radio-frequency transistors and infrared sensors. Control of oxidation-induced changes is essential for decreasing amounts of the harmful InAs surface (or interface) defects because it is hard to avoid the energetically favored oxidation of InAs surface parts in device processing. We have characterized atomic-layer-deposition (ALD) grown Al2O3/InAs interfaces, pre-oxidized differently, with synchrotron hard x-ray photoelectron spectroscopy (HAXPES), low-energy electron diffraction, scanning tunneling microscopy, and time-of-flight elastic recoil detection analysis. The chemical environment and core-level shifts are clarified for well-embedded InAs interfaces (12 nm Al2O3) to avoid, in particular, effects of a significant potential change at the vacuum-solid interface. High-resolution As 3d spectra reveal that the Al2O3/InAs interface, which was sputter-cleaned before ALD, includes +1.0 eV shift, whereas As 3d of the pre-oxidized (3×1)-O interface exhibits a shift of -0.51 eV. The measurements also indicate that an As2O3 type structure is not crucial in controlling defect densities. Regarding In 4d measurements, the sputtered InAs interface includes only a +0.29 eV shift, while the In 4d shift around -0.3 eV is found to be inherent for the crystalline oxidized interfaces. Thus, the negative shifts, which have been usually associated with dangling bonds, are not necessarily an indication of such point defects as previously expected. In contrast, the negative shifts can arise from bonding with O atoms. Therefore, specific care should be directed in determining the bulk-component positions in photoelectron studies. Finally, we present an approach to transfer the InAs oxidation results to a device process of high electron mobility transistors (HEMT) using an As-rich III-V surface and In deposition. The approach is found to decrease a gate leakage current of HEMT without losing the gate controllability.
关键词： synchrotron,oxidation,atomic layer deposition,III-V semiconductor,photoelectron,InAs
更新于2025-09-10 09:29:36
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Characteristics of NiO films prepared by atomic layer deposition using bis(ethylcyclopentadienyl)-Ni and O2 plasma
摘要： Plasma-enhanced atomic layer deposition (PEALD) is well-known for fabricating conformal and uniform films with a well-controlled thickness at the atomic level over any type of supporting substrate. We prepared nickel oxide (NiO) thin films via PEALD using bis(ethylcyclopentadienyl)-nickel (Ni(EtCp)2) and O2 plasma. To optimize the PEALD process, the effects of parameters such as the precursor pulsing time, purging time, O2 plasma exposure time, and power were examined. The optimal PEALD process has a wide deposition-temperature range of 100-325 oC and a growth rate of 0.037±0.002 nm per cycle. The NiO films deposited on a silicon substrate with a high aspect ratio exhibited excellent conformality and high linearity with respect to the number of PEALD cycles, without nucleation delay.
关键词： Thin Film,Nickel Oxide,Plasma-enhanced Atomic Layer Deposition,Bis(ethylcyclopentadienyl)-nickel,Atomic Layer Deposition
更新于2025-09-09 09:28:46
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GaN metal-oxide-semiconductor devices with ZrO2 as dielectric layers
摘要： P-type GaN metal oxide semiconductors (MOS) with ZrO2 dielectrics have been fabricated. Here, H2O and O3 were selected as oxidizers for ZrO2 growth by atomic layer deposition. The MOS devices with O3 oxidant demonstrated a smaller ?at band voltage than that with H2O oxidant. A Ga2O3 interlayer was formed between GaN and O3-grown ZrO2, which can e?ectively decrease interfacial state density to 1.5 × 1011 cm?2. Meanwhile, the innovation of AlZnO (AZO)/Ag nanowires (AgNWs)/AlZnO composite electrodes can further decrease the ?at band voltage to about a half compared to that with traditional Cr/Au electrodes and superior electrical performance was achieved.
关键词： Silver nanowires,MOS,ZrO2,Atomic layer deposition,p-GaN
更新于2025-09-09 09:28:46
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Growth without Postannealing of Monoclinic VO2 Thin Film by Atomic Layer Deposition Using VCl4 as Precursor
摘要： Vanadium dioxide (VO2) is a multifunctional material with semiconductor-to-metal transition (SMT) property. Organic vanadium compounds are usually employed as ALD precursors to grow VO2 films. However, the as-deposited films are reported to have amorphous structure with no significant SMT property, therefore a postannealing process is necessary for converting the amorphous VO2 to crystalline VO2. In this study, an inorganic vanadium tetrachloride (VCl4) is used as an ALD precursor for the first time to grow VO2 films. The VO2 film is directly crystallized and grown on the substrate without any postannealing process. The VO2 film displays significant SMT behavior, which is verified by temperature-dependent Raman spectrometer and four-point-probing system. The results demonstrate that the VCl4 is suitably employed as a new ALD precursor to grow crystallized VO2 films. It can be reasonably imagined that the VCl4 can also be used to grow various directly crystallized vanadium oxides by controlling the ALD-process parameters.
关键词： vanadium tetrachloride,vanadium oxide,atomic layer deposition,semiconductor-to-metal transition,vanadium dioxide
更新于2025-09-09 09:28:46
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[IEEE 2018 33rd Symposium on Microelectronics Technology and Devices (SBMicro) - Bento Gon?alves, Brazil (2018.8.27-2018.8.31)] 2018 33rd Symposium on Microelectronics Technology and Devices (SBMicro) - On the influence of conductor, semiconductor and insulating substrate on the structure of atomic layer deposited titanium dioxide thin films
摘要： Titanium dioxide (TiO2) thin films were deposited on conductive (titanium and fluorine tin oxide glass), insulant (mica, cover glass and thermal SiO2 thin film on silicon) and semiconductive (silicon (100) and 4H-SiC) substrates by atomic layer deposition (ALD) technique. The metal and ligand precursors used were tetrachloride and water, respectively. Grazing incidence x-ray diffraction (GIXRD) analysis was performed to investigate the dependence of crystalline phase of the as-deposited thin films on different substrates for process temperatures ranging from 150-450oC. Results indicate that the ALD TiO2 crystalline phase is dependent on the substrate nature which modifies the required temperature for phase change, i.e. from amorphous to anatase to rutile. For example, for conductive substrates the temperature for formation of rutile phase is around 350 oC while for semiconductor substrates it was observed only from 400oC. By other hand, when the substrate has an amorphous structure there is not a common rule, i.e. for mica and thermal SiO2 thin film on silicon only anatase phase was formed in all temperature range investigated while, for cover glass, it was possible to observe all stages of TiO2 phase change, highlighting the formation of brookite phase for temperatures between 300 and 350°C. Moreover, it is shown that rutile phase can be obtained, in pure phase, at temperatures higher than 400oC, however only for glass and titanium substrates. These results allow us to infer that less expensive Ti thin film could act as a good seed layer for growth of good quality rutile TiO2 phase, by using ALD process on Si substrate and using precursors such as TiCl4 and H2O.
关键词： substrate type,titanium dioxide,GIXRD,atomic layer deposition
更新于2025-09-09 09:28:46
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Band alignment of BiOCl/ZnO core shell nanosheets by X-ray photoelectron spectroscopy measurements
摘要： To improve optoelectronic properties of bismuth oxyhalides, hybrid BiOX photocatalytic materials have draw a great attention, because of the separation of photogenerated electron-hole pairs. The band offset and band alignments are considered as the key parameters to elaborate carrier transport properties in heterojunction. In this paper, to determine the band alignment of BiOCl and ZnO heterostructure, BiOCl/ZnO core shell nanosheets with different thickness of shell layer were synthesized. The valence band offset (VBO or DEV) of BiOCl/ZnO heterostructure was determined using X-ray Photoelectron Spectroscopy measurements. The DEV value of 0.294 § 0.10 eV was calculated by using the Zn 2p3/2, Bi 4f5/2 binding energies as references. Taking the band gaps of 3.37 eV and 3.4 eV for ZnO and BiOCl samples into consideration, respectively, we obtained the type-II band alignment of BiOCl/ZnO heterostructure with a conduction band offset (CBO or DEc) of 0.324 § 0.10 eV.
关键词： X-ray photoelectron spectroscopy (XPS),band offset,BiOCl,ZnO,atomic layer deposition (ALD)
更新于2025-09-09 09:28:46
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Composite GaN-C-Ga (‘GaCN’) Layers with Tuneable Refractive Index
摘要： This article describes novel composite thin films consisting of GaN, C and Ga (referred to as ‘GaCN’, as an analogue to BCN and other carbonitrides) as a prospective material for future optical applications. This is due to their tuneable refractive index that depends on the carbon content. The composites are prepared by introducing alternating pulses of trimethylgallium (TMG) and ammonia (NH3) on silicon substrates to mimic an atomic layer deposition process. Since the GaCN material is hardly reported to the best of our knowledge, a comprehensive characterization is performed to investigate into its chemical nature, primarily to determine whether or not it exists as a single-phase material. It is revealed that GaCN is a composite, consisting of phase-segregated, nano-scale clusters of wurtzitic GaN polycrystals, in addition to inclusions of carbon, nitrogen and gallium, which are chemically bonded into several forms, but not belonging to the GaN crystals itself. By varying the deposition temperature between 400 and 600 oC, and the NH3 partial pressure between 0.7×10-3 and 7.25 mbar, layers with a wide compositional range of Ga, C and N are prepared.
关键词： composite thin films,atomic layer deposition,optical applications,GaCN,tuneable refractive index
更新于2025-09-09 09:28:46
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Development of a scanning probe microscopy integrated atomic layer deposition system for <i>in situ</i> successive monitoring of thin film growth
摘要： A dual chamber system integrated with atomic layer deposition (ALD) and atomic force microscopy (AFM) was developed for the successive monitoring of nanoparticles to thin film growth process. The samples were fabricated in the ALD chamber. A magnetic transmission rod enabled sample transferring between the ALD and the AFM test chambers without breaking the vacuum, avoiding possible surface morphology change when frequently varying the growth condition and oxidation under ambient condition. The sample transmission also avoids deposition and contamination on the AFM tip during the successive testing. The sample stage has machined a group of accurate location pinholes, ensuring the 10 μm2 measurement consistency. As a demonstration, the platinum thin films with different thickness were fabricated by varying ALD cycles. The surface morphology was monitored successively during the deposition. Under vacuum with controlled oxygen partial pressure, the aging and sintering phenomenon of particles has been studied in the AFM testing chamber after high temperature treatment. The integrated AFM/ALD instrument is potentially a powerful system for monitoring the thin film preparation and characterization.
关键词： platinum thin films,atomic force microscopy,in situ monitoring,atomic layer deposition,thin film growth
更新于2025-09-04 15:30:14