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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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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