Sn Diffusion Research Articles

Diffusion of Ge Donors in β‐Ga2O3

Diffusion of Ge donors in β‐Ga2O3 is studied using a combination of secondary‐ion mass spectrometry, diffusion simulations, and first‐principles calculations, and compared to previous studies on Sn diffusion. Ge is implanted into (01)‐oriented samples and annealed at temperatures from 900 to 1050 °C for a total of 8 h. From previous first‐principles calculations, Sn is predicted to diffuse via the formation of a mobile complex with VGa that migrates through a sequence of exchange and rotation jumps. Herein, it is similarly predicted that Ge diffusion is mediated by VGa. However, the microscopic mechanism differs, as Ge can diffuse more easily through exchange combined with complex dissociation, rather than rotational jumps. This is explained by the difference in Ga‐site preference of Ge compared to Sn, and the three‐split mechanism that enables low migration barriers for VGa. The dissociation mechanism leads to a considerably faster transport for Ge as compared to Sn. The experimentally obtained Ge diffusion profiles are successfully fitted using a reaction–diffusion model based on the predicted diffusion mechanism, yielding a migration barrier of 2.5 ± 0.2 eV for the complex. The 2.72 eV obtained from first‐principles calculations is in good agreement with this value.

First demonstration of Sn diffusion into gallium oxide from poly-tetraallyl tin deposited by initiated chemical vapor deposition by thermal treatment

Gallium oxide (Ga2O3) is attracting attention as a next-generation semiconductor material for power device because it has a wide energy band gap and high breakdown electric field. We deposited a Sn polymer, poly-tetraallyl tin, on Ga2O3samples using a disclosed initiated chemical vapor deposition (iCVD) process. The Sn dopant of the Sn polymer layer is injected into the Ga2O3through a heat treatment process. Diffusion model of Sn into the Ga2O3is proposed through secondary ion mass spectroscopy analysis and bond dissociation energy. The fabricated device exhibited typical n-type field-effect transistor (FET) behavior. Ga2O3Sn-doping technology using iCVD will be applied to 3D structures and trench structures in the future, opening up many possibilities in the Ga2O3-based power semiconductor device manufacturing process.

(Invited) Efficient P-Doping Via Suppressing Bad P−Sn Interaction

The utilization of non-metallic phosphorus (P) doping is recognized for its advantages in enhancing the conductivity of hematite while minimizing recombination. This is attributed to the suppression of electron trapping facilitated by the favorable electron state of P5+. However, our investigation reveals a significant impact on the overall photoelectrochemical (PEC) performance of P-doped Fe2O3 due to tin (Sn) diffusion from the bottom FTO substrate. Upon identifying the unfavorable interaction between the unintentional dopant Sn4+ and intentional dopant P5+, we have developed a straightforward P-doping method. The resulting P:Sn:Ti-Fe2O3 (P:Sn:Ti triple-doped Fe2O3) exhibits a remarkable improvement in photocurrent density, reaching 3.44 mA cm−2 at 1.23 VRHE, surpassing values reported in previous P-doping hematite studies. Following co-catalyst deposition, the NiFeOx/P:Sn:Ti-Fe2O3 photoanode achieves a maximum photocurrent density of 4.30 mA cm−2 at 1.23 VRHE. This study affirms that suppressing the negative interaction between dopants is crucial for significantly enhancing PEC performance.

Diffusion Barrier Performance of Ni-W Layer at Sn/Cu Interfacial Reaction.

As the integration of chips in 3D integrated circuits (ICs) increases and the size of micro-bumps reduces, issues with the reliability of service due to electromigration and thermomigration are becoming more prevalent. In the practical application of solder joints, an increase in the grain size of intermetallic compounds (IMCs) has been observed during the reflow process. This phenomenon results in an increased thickness of the IMC layer, accompanied by a proportional increase in the volume of the IMC layer within the joint. The brittle nature of IMC renders it susceptible to excessive growth in small-sized joints, which has the potential to negatively impact the reliability of the welded joint. It is therefore of the utmost importance to regulate the formation and growth of IMCs. The following paper presents the electrodeposition of a Ni-W layer on a Cu substrate, forming a barrier layer. Subsequently, the barrier properties between the Sn/Cu reactive couples were subjected to a comprehensive and systematic investigation. The study indicates that the Ni-W layer has the capacity to impede the diffusion of Sn atoms into Cu. Furthermore, the Ni-W layer is a viable diffusion barrier at the Sn/Cu interface. The "bright layer" Ni2WSn4 can be observed in all Ni-W coatings during the soldering reflow process, and its growth was almost linear. The structure of the Ni-W layer is such that it reduces the barrier properties that would otherwise be inherent to it. This is due to the "bright layer" Ni2WSn4 that covers the original Ni-W barrier layer. At a temperature of 300 °C for a duration of 600 s, the Ni-W barrier layer loses its blocking function. Once the "bright layer" Ni2WSn4 has completely covered the original Ni-W barrier layer, the diffusion activation energy for Sn diffusion into the Cu substrate side will be significantly reduced, particularly in areas where the distortion energy is concentrated due to electroplating tension. Both the "bright layer" Ni2WSn4 and Sn will grow rapidly, with the formation of Cu-Sn intermetallic compounds (IMCs). At temperatures of 250 °C, the growth of Ni3Sn4-based IMCs is controlled by grain boundaries. Conversely, the growth of the Ni2WSn4 layer (consumption of Ni-W layer) is influenced by a combination of grain boundary diffusion and bulk diffusion. At temperatures of 275 °C and 300 °C, the growth of Ni3Sn4-based IMCs and the Ni2WSn4 layer (consumption of Ni-W layer) are both controlled by grain boundaries. The findings of this study can inform the theoretical design of solder joints with barrier layers as well as the selection of Ni-W diffusion barrier layers for use in different soldering processes. This can, in turn, enhance the reliability of microelectronic devices, offering significant theoretical and practical value.

The tin content of lead inclusions in ancient tin-bronze artifacts: a time-dependent process?

In antiquity, Pb was a common element added in the production of large bronze artifacts, especially large statues, to impart fluidity to the casting process. As Pb does not form a solid solution with pure Cu or with the Sn–Cu alloy phases, it is normally observed in the metal matrix as globular droplets embedded within or in interstitial positions among the crystals of Sn-bronze (normally the α phase) as the last crystallizing phase during the cooling process of the Cu–Sn–Pb ternary melt. The disequilibrium Sn content of the Pb droplets has recently been suggested as a viable parameter to detect modern materials [Shilstein, Berner, Feldman, Shalev & Rosenberg (2019). STAR Sci. Tech. Archaeol. Res. 5, 29–35]. The application assumes a time-dependent process, with a timescale of hundreds of years, estimated on the basis of the diffusion coefficient of Sn in Pb over a length of a few micrometres [Oberschmidt, Kim & Gupta (1982). J. Appl. Phys. 53, 5672–5677]. Therefore, Pb inclusions in recent Sn-bronze artifacts are actually a metastable solid solution of Pb–Sn containing ∼3% atomic Sn. In contrast, in ancient artifacts, unmixing processes and diffusion of Sn from the micro- and nano-inclusions of Pb to the matrix occur, resulting in the Pb inclusions containing a substantially lower or negligible amount of Sn. The Sn content in the Pb inclusions relies on accurate measurement of the lattice parameter of the phase in the Pb–Sn solid solution, since for low Sn values it closely follows Vegard's law. Here, several new measurements on modern and ancient samples are presented and discussed in order to verify the applicability of the method to the detection of modern artwork pretending to be ancient.

Effects of high-temperature annealing on vacancy complexes and luminescence properties in multilayer periodic structures with elastically strained GeSiSn layers

Effects of postgrowth high-temperature annealing on vacancy complexes and photoluminescence (PL) from GeSiSn/Si multiple quantum wells (MQWs) are studied. The series of PL peaks related to the vacancy-tin complexes was observed for as-grown samples including different structures, such as GeSiSn/Si MQWs, multilayer periodic structure with GeSiSn quantum dots (QDs), GeSn cross-structures upon GeSiSn/Si MQWs, and thick GeSiSn layers. The PL band intensity is significantly reduced after annealing at 700 °C corresponding to the reduction in vacancy density, as demonstrated by the positron annihilation spectroscopy (PAS) data. Such annealing also results in the appearance of the PL signal related to the interband optical transitions in GeSiSn/Si MQWs. However, the high temperature could negatively impact the sharpness of heterointerfaces due to Sn diffusion, thus limiting the PL efficiency. To improve the luminescence properties of GeSiSn/Si structures, we proposed a two-stage technique combining both the annealing and subsequent treatment of samples in a hydrogen plasma at 200 °C. The plasma treatment significantly reduces the PL band of vacancy-related defects, whereas annealing at a moderate temperature of ∼600 °C prevents the blurring of heterointerfaces. As a result, we demonstrate an increase in the relative efficiency of interband PL of type II GeSiSn/Si MQW structures emitting in the range of 1.5–2 μm.

Deposition of Fe2O3:Sn semiconducting thin films by reactive pulsed HiPIMS + ECWR co-sputtering from Fe and Sn targets

Semiconducting Fe2O3 thin films were deposited on SnO2:F (FTO) and Pt substrates by reactive high-power impulse magnetron sputtering combined with electron cyclotron wave resonance plasma (HiPIMS + ECWR). Fe2O3 films were fabricated either by sputtering from a single Fe target or by co-sputtering from an additional Sn target. Plasma parameters during co-sputtering were measured by an RF probe system enabling the comparison between HiPIMS + ECWR and only HiPIMS conditions used for the film deposition. As deposited Fe2O3 films were post-annealed in air at 450 °C and 650 °C, respectively. It was shown that as deposited Fe2O3 films were amorphous but became crystalline after post-annealing at 450 °C. Further increase of annealing temperature to 650 °C did not improve significantly the crystalline structure of the Fe2O3 film. All post-annealed Fe2O3 films exhibited photocurrents in the anodic region; generally, hematite films annealed at 650 °C exhibited higher photocurrents than those annealed at 450 °C. Films doped by Sn co-sputtering had higher photocurrents than films only doped by Sn diffusion during post-annealing from the FTO substrate. Hematite films on Pt substrate doped by Sn co-sputtering and post-annealed at 650 °C exhibited the highest photocurrents. It was verified by XPS analysis with ion sputtering depth profiling that Pt atoms also diffuse from the Pt substrate into the Fe2O3 film during the post-annealing at 650 °C and can, similar to Sn in the case of an FTO substrate, act as a dopant.

Design of metallization layers for PZT piezoelectric ceramics and joining to 4J29 Kovar alloy

To enhance the bonding strength of PZT ceramics/4J29 Kovar alloy joints, the metallization layers on PZT ceramics were strategically designed, fabricated, and optimized. Subsequently, the metallized PZT ceramics were successfully joined with the 4J29 Kovar alloy using Sn-3.0Ag-0.5Cu (SAC305) solder. In this study, the wetting behavior, joining mechanism and the effect of metallization layers thickness on the joining strength were investigated. The (Ti + Ni + Au) multilayer structure enhances wetting, as Au dissolves into the solder to improve wetting, while Ni serves as a barrier to prevent direct contact between the solder and Ti, thereby ensuring the integrity of the metallization layer. The joining mechanism for PZT ceramics/solder and solder/4J29 Kovar alloy involves the reaction between Ni (in the metallization layer) and Sn (in the solder), and Sn diffusion into 4J29 Kovar alloy, respectively. The highest joint strength of 29.0±1.4 MPa was achieved with (Ti + Ni + Au) metallization layers (Ti:100 nm, Ni:1000 nm, Au:300 nm), marking a 120% improvement over the adhesive currently used for joining PZT ceramics to 4J29 Kovar alloy. Our work presents a promising method for joining PZT ceramics with 4J29 Kovar alloy, which is applied in transducers as a core component for oil logging.

Atomic Diffusion Engineered PtSnCu Nanoframes with High-Index Facets Boost Ethanol Oxidation.

Electrochemical ethanol oxidation is crucial to directly convert a biorenewable liquid fuel with high energy density into electrical energy, but it remains an inefficient reaction even with the best catalysts. To boost ethanol oxidation, developing multimetallic nanoalloy has emerged as one of the most effective strategies, yet faces a challenge in the rational engineering of multimetallic active-site ensembles at atomic-level. Herein, starting from typical PtCu nanocrystals, an atomic Sn diffusion strategy is developed to construct well-defined Pt47Sn12Cu41 octopod nanoframes, which is enclosed by high-index facets of n (111)-(111), such as {331} and {221}. Pt47Sn12Cu41 achieves a high mass activity of 3.10 A mg-1 Pt and promotes the C-C bond breaking and oxidation of poisonous CO intermediate, representing a state-of-the-art electrocatalyst toward ethanol oxidation in acidic electrolyte. Density functional theory （DFT） calculations have confirmed that the introduction of Sn improves the electroactivity by uplifting the d-band center through the s-p-d coupling. Meanwhile, the strong binding of ethanol and the reduced energy barrier of CO oxidation guarantee a highly efficient ethanol oxidation process with improved Faradic efficiency of C1 products. This work offers a promising strategy for constructing novel multimetallic nanoalloys tailored by atomic metal sites as the efficient electrocatalysts.

On the surface segregation of Sn in cold-rolled Fe under continuous annealing conditions

The surface segregation of Sn in cold-rolled Fe-0.03Sn and Fe-0.01Sn (at.%) model alloys was investigated for annealing parameters characteristic of continuous galvanizing lines (CGLs). The most significant increase in surface coverage occurred during linear heating between 500 and 675 °C, where no significant change in segregation was observed with isothermal holding for 60 – 480 s at peak annealing temperatures of 675 – 825 °C. While the bulk diffusion of Sn in Fe determined the segregation rate during extended isothermal holding up to 10800 s, it could not account for the rapid increase in coverage during heating. It was determined that Sn segregation was accelerated during linear heating by rapid diffusion along dislocation pipes in the cold-rolled starting microstructure. Integrating the decrease in diffusivity due to recrystallization into the McLean model for interfacial segregation resulted in an experimentally verified description of segregation kinetics during linear heating. It was also able to predict the experimentally observed increase in segregation when the linear heating rate between 500 °C and 675 °C was decreased from 5 to 1 °C/s. No significant difference in surface segregation was observed between the 0.01 and 0.03 at.% Sn addition for isothermal holding of 480 s or less, which can be explained by the saturation of easy adsorption sites. A bond-breaking model was used to illustrate their origin from imperfect coordination within the surface layer. As significant surface segregation can be achieved within the CGL processing window, Sn microalloying appears as a promising strategy to improve galvanized coating quality.

Surface treatment by crystalline Co-P coating with ultra-thin CoTe2 layer for improved electrical and mechanical properties of the n-type Bi2Te3/Sn TEG electrode

Bismuth telluride-based thermoelectric generators (TEG) were widely used in the clean recovery of waste heat, but frequent failure problems at the hot-end electrode interface limited the reliable service of TEGs. Diffusion at the electrode interface between n-type Bi2Te3 and Sn-based solder seriously damaged the performance of the TEGs. In this work, the crystalline Co-4 at.% P coating was deposited to protect the n-type thermoelectric material Bi2Te3. The microstructural characterization proved that the Co-P coating effectively resisted the diffusion of Sn, Bi, Te and Cu atoms, and prevented the generation of brittle intermetallic compounds (IMC) and cracks at the interface. Ultra-thin CoTe2 layer was formed between Co-P and Bi2Te3, much thinner than the brittle Ni-Te layer reported in the literatures. It not only showed that a good metallurgical bond was formed between Co-P and Bi2Te3, but also implied the Co-P only consumed little thermoelectric elements. After the 150-hour aging test at 423 K, the shear strength of the electrode joints did not decrease, and the power generation sustainability of thermoelectric pillars was significantly improved compared with uncoated pillars. Overall, the crystalline Co-P coating would be an excellent candidate to protect the n-type Bi2Te3 pillars of the TEGs.

Evidences for diffusion-induced phase evolution and crack generation of intermetallic at Bi2Te3/Sn interface of thermoelectric generator electrode

Bismuth telluride-based thermoelectric generators (TEG) were widely used in waste heat recovery, but the failure problem at the electrode interface was serious, which was related to the severe diffusion between Sn and Bi2Te3. However, the diffusion behavior and process have not been reasonably evaluated and mechanism analyzed, which was not conducive to the design and improvement of TEGs. In this work, hot-end electrode aging was performed at 150 °C, and the diffusion, intermetallic compounds (IMC), as well as crack induction between Bi2Te3 and Sn-based solder were systematically investigated. It was found that the interdiffusion of Sn and Te atoms led to the formation of Bi2Te with HCP structure and SnTe with FCC structure at the interface. Bi2Te was a Bi-rich layer formed after the migration of Te atoms away from Bi2Te3, and SnTe had a double-layer structure respectively attributing to the diffusion of Sn and Te atoms. Diffusion-induced cracks tended to occur at Bi2Te/SnTe interfaces and SnTe/Sn interfaces. The former was related to the diffusion-induced phase transformation at the diffusion front of Sn atoms, while the latter generated from the initiation and expansion of Kirkendall voids. In addition, the brittleness of the Bi-rich phase aggravated the crack propagation. The shear test results of the electrodes confirmed that these cracks were the weakness of TEG electrodes. It was recommended to introduce a barrier layer at the interface to provide protection, and the fabrication of direct soldering was not suggested.

Enhancing power generation sustainability of thermoelectric pillars by suppressing diffusion at Bi-Sb-Te/Sn electrode interface using crystalline Co-P coatings

Bismuth telluride-based thermoelectric (TE) devices were widely used in waste heat recovery due to their high thermoelectric figure of merit (ZT), but the severe diffusion between Sn-based solder and TE pillar generated porous and brittle Sn-Te intermetallic compound (IMC), which seriously restricted the reliable service of devices. Ni-based coating was used but the thick Ni-Te IMC also impaired the properties of TE pillars. In this work, the crystalline Co-P coating was inserted between the p-type TE material Bi0.5Sb1.5Te3 and the solder by electrodeposition, and the power generation sustainability of the TE pillar were significantly improved, and the mechanism was revealed. The microstructural characterization proved that the Co-P coating could effectively resist the diffusion of active Sn, Bi, Sb, Cu atoms. Co-P coating would provide support for the structural integrity and performance sustainability of TE pillars. It was worth noting that an ultrathin CoTe2 IMC layer was formed between the Co-P coating and the Bi-Sb-Te pillar, which was much thinner than the Ni-Te IMC layer reported in the literature. This indicated that Co-P only consumed little thermoelectric elements, but also a good metallurgical bond was formed between the Co-P and the Bi-Sb-Te. After aging at 423 K for 150 h, the maximum output power and average Seebeck coefficient of the TE pillar without coating dropped significantly by 74% and 34%, respectively, and the internal resistance rose by 67%. Remarkably, the maximum output power and average Seebeck coefficient of the TE pillar protected by the Co-P coating only decreased by 14% and 5%, respectively, and the internal resistance only increased by 6%.

Impact of Sn incorporation on sputter epitaxy of GeSn

Epitaxial growth of high-quality low tin content germanium (GeSn) alloy is demonstrated by sputter deposition. Adding several percent of Sn during simultaneous sputter deposition significantly improved the crystallographic structure of the GeSn alloy, leading to intense photoluminescence even at room temperature. Dislocation-free single-crystal GeSn films were formed on a Ge(100) substrate under tuned growth conditions, that is, an Sn/Ge flux ratio of 6.2% and deposition temperature of 500 °C, in which compositional gradation of the Sn content in the film thickness direction spontaneously formed. The growth mechanisms are discussed based on growth kinetics and Sn diffusion on the growing surface.

Role of dislocations on Sn diffusion during low temperature annealing of GeSn layers

A study of the mechanism of Sn out-diffusion was performed by annealing Ge0.905Sn0.095 layers at 300 °C. The changes in Sn composition and strain state were confirmed by x-ray diffraction and photoluminescence spectroscopy. Surface defects, appearing as Sn particles, with the highest density of 3.5 × 108 cm−2 were detected by atomic force microscopy after annealing for 2 h. The strain in the GeSn layer stabilized for more prolonged annealing, while the density of particles decreased and their size increased. Annealing results are discussed in terms of Sn segregation and subsequent diffusion along dislocation lines, enhanced out-diffusion by dislocations migration, and surface particle coalescence.

Study on the dissolution diffusion behavior of Al in Sn melt

The Al-Sn alloys with a large melting point difference and large density are widely used in sliding bearings in the aerospace and automobile industries. But the problem of insufficient alloying easily occurs during the preparation process due to the physical properties. This paper investigates the dissolution and diffusion behavior of Al in Sn Melt. The dissolution rates of Al in Sn melts at different temperatures were calculated. The research results show that the Al/Sn diffusion is dominated by the diffusion of Sn into Al, the Sn melt penetrate into the solid Al to form diffusion channel leading to the exfoliation and aggregation of the unmelted Al particles. Then, an electromagnetic field treatment technology was introduced to improve sufficient alloying by regulating the flow field of the metal melt. It can accelerate the diffusion and redistribution of elements at the Al/Sn solid-liquid interface, as well as change the dissolution mechanism of Al/Sn interface.

Thermodynamic route of Nb3Sn nucleation: Role of oxygen

Intermetallic Nb3Sn alloys have long been believed to form through Sn diffusion into Nb. However, our observations of significant oxygen content in Nb3Sn prompted an investigation of alternative formation mechanisms. Through experiments involving different oxide interfaces (clean HF-treated, native oxidized, and anodized), we demonstrate a thermodynamic route that fundamentally challenges the conventional Sn diffusion mechanism for Nb3Sn nucleation. Our results highlight the critical involvement of a SnOx intermediate phase. This new nucleation mechanism identifies the principles for growth optimization and new synthesis of high-quality Nb3Sn superconductors.

Self-toughening mechanism of the ZrO2 scale and the precipitation of Sn during the steam oxidation of ZIRLO™ at 1200 °C

The steam oxidation behavior of ZIRLO™ at 1200 °C was investigated using a thermogravimetric analyzer. The microstructure of the oxide was analyzed using SEM, EBSD, and FIB+TEM in depth. Very long “spaghetti-like” columnar oxide grains were formed owing to the intracrystalline diffusion of O2− and the high oxidation temperature. These grains extended from the oxide/matrix interface to a thin outer equiaxed grain layer. The special growth mechanism of the columnar grains determines the unique properties of the oxide scale, such that their structural integrity cannot be destroyed. Therefore, the oxidation kinetics followed a parabolic law throughout the oxidation process without breakaway behavior. Observations revealed the presence of twins, slip bands, and subgrains within the ZrO2 grains, which were identified as the primary manners of oxide deformation under stress. The residual stress and phase distribution along the thickness of the oxide were investigated using synchrotron radiation X-ray diffraction. The oxide was almost completely transformed into a m phase after oxidation. The compressive stress inside the oxide was relatively low, indicating that the stress was relaxed. Transformation toughening, plastic deformation, densely arranged columnar grains, and the absence of grain boundaries parallel to the direction of compressive stress constitute the self-toughening mechanism of the ZrO2 scale. Zr5Sn3, ZrSn2, and β-Nb second phase particles were observed at the ZrO2 grain boundaries and inside the ZrO2 grains. The outward diffusion of Sn in the liquid state and the peritectic reaction can result in the formation of voids at the edges of the second phase particles.

Atomic behavior of Ti in A15 Nb3Sn and its effects on diffusional growth of Nb3Sn layer

Atomic details of the dramatic increase in the diffusional growth rate of A15 Nb3Sn superconducting compound with Ti addition have been investigated using atomistic simulations and experimental observations. Ti atoms preferentially locate at Nb sites in the Nb3Sn bulk while they do not affect the volume diffusion of Sn significantly. In addition, Ti is predicted to segregate on Nb3Sn grain boundaries, inducing the segregation of Sn, but cannot enhance the grain boundary diffusion of Sn enough to explain the dramatic increase in the growth rate of the Nb3Sn layer. On the other hand, grain refinement is observed when Ti is added, which is expected to substantially promote the effective diffusion of Sn. Consequently, grain refinement due to the grain boundary segregation of Ti is revealed as the most important mechanism underlying the alloying effect of Ti. A basic understanding of the atomic behavior of alloying elements in Nb3Sn and clarified alloying effects on the diffusional growth of Nb3Sn compounds will contribute to further investigation of optimal alloying strategies.

Diffusion of Sn donors in β-Ga2O3

Diffusion of the n-type dopant Sn in β-Ga2O3 is studied using secondary-ion mass spectrometry combined with hybrid functional calculations. The diffusion of Sn from a Sn-doped bulk substrate with surface orientation (001) into an epitaxial layer is observed after heat treatments in the temperature range of 1050–1250 °C. Calculated formation energies of Sn-related and intrinsic defects show that the migration of Sn is mediated by Ga vacancies (VGa) through the formation and dissociation of intermittent mobile VGaSnGa complexes. The evolution of the Sn concentration vs depth profiles after heat treatments can be well described by a reaction–diffusion model. Using model parameters guided by the hybrid functional calculations, we extract a VGaSnGa complex migration barrier of 3.0 ± 0.4 eV with a diffusion coefficient of 2 × 10−1 cm2/s. The extracted migration barrier is consistent with our theoretical predictions using the nudged elastic band method, which shows migration barriers of 3.42, 3.15, and 3.37 eV for the [100], [010], and [001] directions, respectively.