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Run-to-run control of PECVD systems: Application to a multiscale three-dimensional CFD model of silicon thin film deposition
摘要： Deposition of amorphous silicon thin films via plasma-enhanced chemical vapor deposition (PECVD) and batch-to-batch operation under run-to-run control of the associated chambered reactor are presented in this work using a recently developed multiscale, three-dimensional in space, computational fluid dynamics model. Macroscopic reactor scale behaviors are linked to the microscopic growth of amorphous silicon thin films using a dynamic boundary which is updated at each time step of the transient in-batch simulations. This novel workflow is distributed across 64 parallel computation nodes in order to reduce the significant computational demands of batch-to-batch operation and to allow for the application and evaluation in both radial and azimuthal directions across the wafer of a benchmark, run-to-run based control strategy. Using 10 successive batch deposition cycles, the exponentially weighted moving average algorithm, an industrial standard, is demonstrated to drive all wafer regions to within 1% of the desired thickness set-point in both radial and azimuthal directions across the wafer surface. This is the first demonstration of run-to-run control in reducing azimuthal film nonuniformity. Additionally, thin film uniformity is shown to be improved for poorly optimized PECVD geometries by manipulating the substrate temperature alone, without the need for re-tooling of the equipment.
关键词： thin film silicon solar cells,parallel computing,multiscale modeling,computational fluid dynamics,run-to-run control,thin film growth
更新于2025-09-23 15:21:21
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Pulsed-laser epitaxy of metallic delafossite PdCrO <sub/>2</sub> films
摘要： Alternate stacking of a highly conducting metallic layer with a magnetic triangular layer found in delafossite PdCrO2 provides an excellent platform for discovering intriguing correlated quantum phenomena. Thin film growth of delafossites may enable not only the tuning of the basic physical properties beyond what bulk materials can exhibit, but also the development of novel hybrid materials by interfacing with dissimilar materials, yet this has proven to be extremely challenging. Here, we report the epitaxial growth of metallic delafossite PdCrO2 films by pulsed laser epitaxy (PLE). The fundamental role of the PLE growth conditions, epitaxial strain, and chemical and structural characteristics of the substrate is investigated by growing under various growth conditions and on various types of substrates. While strain plays a large role in improving the crystallinity, the direct growth of epitaxial PdCrO2 films without impurity phases was not successful. We attribute this difficulty to both the chemical and structural dissimilarities with the substrate and volatile nature of the PdO sublayer, which make nucleation of the right phase difficult. This difficulty was overcome by growing CuCrO2 buffer layers before PdCrO2 films were grown. Unlike PdCrO2, CuCrO2 films were readily grown with a relatively wide growth window. Only a monolayer thick buffer layer was sufficient to grow the correct PdCrO2 phase. This result indicates that the epitaxy of Pd-based delafossites is extremely sensitive to the chemistry and structure of the interface, necessitating near perfect substrate materials. The resulting films are commensurately strained and show an antiferromagnetic transition at 40 K that persists down to as thin as 3.6 nm in thickness. This work provides key insights into advancing the epitaxial growth of the broader class of metallic delafossites for both studying the basic physical properties and developing new spintronic and computing devices.
关键词： delafossite,pulsed laser epitaxy,thin film growth,antiferromagnetic transition,PdCrO2
更新于2025-09-23 15:21:01
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Thioacetamide additive assisted crystallization of solution-processed perovskite films for high performance planar heterojunction solar cells
摘要： High-quality perovskite films with uniform coverage and large grains are indispensable to enhance the performance of perovskite solar cells with high efficiency and stability. However, solution-processed perovskite films usually possess small grains associated with abundant grain boundaries, which induce high trap state density and then seriously degrade the device performance. In this paper, the volatile Lewis base, thioacetamide (TAA), is employed as an additive to fabricate high-quality methylammonium lead iodide (MAPbI3) films. The average grain size of perovskite films increases continuously with increasing TAA content and reaches a maximum value of 960 nm in the sample with 1.0% TAA. However, the average gain size drops dramatically to the value of samples without TAA when TAA content increases to 2.0%, and then the average gain size keeps nearly unchanged upon further increasing TAA content up to 10%. This unusual grain size variation tendency is attributed to the volatility of additive, and a mechanism is proposed based on various characterizations to illustrate how volatile TAA improves perovskite film crystallization. Furthermore, the device based on the MAPbI3 film with 1.0% TAA shows a superior PCE of 18.9% and improved stability that the device with 1.0% TAA retains 88.9% of its initial performance after aging 816 h in the air with 25–35% relative humidity. The results strongly suggest that the TAA-modified MAPbI3 films as absorber layers can significantly enhance the performance of the perovskite solar cell due to large grains, high crystallization and reduced trap state density of the high quality TAA-modified MAPbI3 films.
关键词： Perovskite solar cells,Thioacetamide,Large grains,Lewis base,Thin film growth
更新于2025-09-19 17:13:59
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Atomistic kinetic Monte Carloa??Embedded atom method simulation on growth and morphology of Cua??Zna??Sn precursor of Cu <sub/>2</sub> ZnSnS <sub/>4</sub> solar cells
摘要： An atomistic kinetic Monte Carlo coupled with the embedded-atom method is used to simulate film growth and morphology evolution of a Cu–Zn–Sn precursor of Cu2ZnSnS4 solar cells by single-step electrodeposition. The deposition and diffusion events of three different metallic atoms are described by the simulation. Moreover, the multibody Cu–Zn–Sn potential is used to calculate diffusion barrier energy. The effects of process factors, including temperature and electrode potential, on the cross-section morphology and surface roughness are explored, while keeping the elemental composition ratios constant. The lowest roughness with the smoothest morphology is obtained at the optimal parameters. The distribution and transformation behaviors of cluster sizes are investigated to describe the alloy film growth process. Furthermore, the comparison between deposition events and diffusion events reveals that deposition events depend primarily on individual deposition rates of different metallic atoms, but diffusion events are mainly dependent on the interaction of metallic atoms. The film morphology evolution is visualized by three-dimensional configuration with increasing numbers of atoms, which suggests a competing mechanism between nucleation and growth of the thin film alloy.
关键词： Cu–Zn–Sn precursor,film growth,Cu2ZnSnS4 solar cells,electrodeposition,atomistic kinetic Monte Carlo,morphology evolution,embedded-atom method
更新于2025-09-16 10:30:52
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Modified Stack Layer for a Two-Step Process for High Efficiency CZTSe Solar Cell
摘要： For kesterite Cu2ZnSnSe4 (CZTSe) solar cells, the CZTSe absorber is usually fabricated using a two-step process, in which the CZTSe absorber is made by using post-selenization of a sputtered metal stack ?lm. In the post-selenized CZTSe ?lm, a rough surface, voids, and small-grained structures at bottom near the Mo back contact are frequently observed. To avoid these inferior features, we designed and fabricated a new modi?ed stack layer that showed compact and larger grains with no voids and with small-grain-free near the bottom side. Several measurements, such as X-ray di?raction, Raman spectroscopy, photoluminescence, and time-resolved photoluminescence measurements, showed that the selenized ?lm from the newly designed stack layer had high crystal quality. With the fabricated absorber, we made two types of CZTSe solar cells, one with a CdS bu?er and the other with a (Zn,Sn)O bu?er. The (Zn,Sn)O- bu?ered CZTSe solar cell showed a power conversion e?ciency of 8.31%, which is comparable to the 8.84% of the CdS-bu?ered CZTSe solar cell. Our results indicates that the CZTSe solar cells made by using our newly designed stack layer and a (Zn,Sn)O bu?er are promising for high-e?ciency Cd-free CZTSe solar cells.
关键词： Film growth,Stack layer,CZTSe,Solar cell
更新于2025-09-12 10:27:22
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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