Post Oxidation Research Articles

Laser damage and post oxidation repair performance of n-TOPCon solar cells with laser assisted doping boron selective emitter

Boron laser-assisted doped selective emitter (LDSE) is a research hotspot in the mass production of N-type tunnel oxide passivated contact (TOPCon) silicon solar cells. Consequently, it is critical to investigate the damage and repair of laser-assisted doped selective emitter. Through simulation, a surface temperature of silicon rises to over 1414 °C during the laser-assisted doping process, which causes silicon to melt and recrystallize more quickly, and increases the solid solubility of B atoms. Meanwhile, the surface pyramid structure was partially destroyed or even collapsed. The results showed that the peak intensity of (211) crystal planes decreased while the peak intensity of (400), (311), and (220) crystal planes increased. This led to an increase in surface defects and suspension bonds, resulting in an increase in J0,passivated up to 246.3 fA/cm2. The laser-induced damage can be successfully repaired by the post-oxidation process, reducing J0,passivated to 45.07 fA/cm2. The Quokka simulation indicates that a laser pulse fluence of 2.78 J/cm2 can increase the efficiency of the LDSE cell by 0.31 %. It does not necessarily lead to the greater efficiency gains with higher laser pulse fluence owing to the increase in surface damage. Exploiting the laser assisted doping method with a minimal surface damage, a wide process window and low cost will be the next major challenge.

Cost-Effective Fabrication of Polydimethylsiloxane (PDMS) Microfluidics for Point-of-Care Application

Microfluidics fabrication pertains to the construction of small-scale devices and systems that manipulate and control small volumes of fluids. This process involves precise engineering and manufacturing procedures aimed at designing and producing these devices, which find applications in healthcare, environmental monitoring, and chemical analysis. The present study showcases an inexpensive approach to fabricate microfluidics channels using PDMS biopolymer and soft lithography technique to achieve laminar fluid flow. Initially, a robust and adhesive mold was created by fabricating a master template using several layers of SU-8 5 and SU-8 2015 negative photoresists. Subsequently, PDMS microfluidics channels were replicated and sealed onto a glass substrate through plasma bonding treatment. High-power microscopy images and profilometer analyses demonstrated successful fabrication with minimal deviation from the initial designs and the fabricated devices (less than 0.07 mm, less than 0.6°). Both the SU-8 master template and PDMS replicate displayed average microchannel height values and surface roughness of 100 μm and 0.26 μm or lower, respectively. Additionally, the fluid test confirmed laminar flow without any leakage post plasma oxidation, indicating the completion of an efficient and cost-effective fabrication process.

Electrically active defects induced by thermal oxidation and post-oxidation annealing of n-type 4H-SiC

In this work, we have performed a detailed study of the defects created in the bulk of 4H-SiC after thermal oxidation and post oxidation annealing using deep level transient spectroscopy and minority carrier transient spectroscopy (MCTS). The study reveals the formation of several shallow and deep level majority carrier traps in the bandgap. The ON1 (EC−0.85 eV), ON2a (EC−1.05 eV), and ON2b (Ec−1.17 eV) levels are the most dominant and are observed across all the samples (EC denotes the conduction band edge). Three shallow levels Ti(k) (EC−0.17 eV), E0.23 (EC−0.23 eV), and C1/2 (EC−0.36/0.39 eV) are observed in the samples. For most of the majority carrier defects, the highest concentration is observed after an NO anneal at 1300°C. This behavior is sustained in the depth profile measurements where the defect concentration after the NO anneal at 1300°C is significantly higher than for the rest of the samples. The origin of most of the majority carrier defects has been attributed to C interstitial injection from the interface during thermal oxidation and annealing. MCTS measurements reveal two prominent minority carrier traps, labeled O0.17 (EV+0.17 eV) and B (EV+0.28 eV), where the concentration of O0.17 is independent of annealing parameters while the concentration of the B level increases after the NO anneal (EV denotes the valence band edge). Furthermore, the depth profiles of the defects are used to evaluate their diffusion parameters by solving the diffusion equation to fit the experimental profiles. The defect concentrations decay exponentially with depth, which evidences that the defects were created at or near the SiO2–SiC interface and migrate toward the bulk during oxidation and post-oxidation annealing.

Effect of Nitrocarburizing and Post-oxidation Processes on the Microstructure and Surface Properties of AISI 4140 Steel

AISI 4140 çeliği, orta karbonlu düşük alaşımlı çelikler sınıfında yer almakta olup, yüksek sertleşebilirliğe sahip olması ve nispeten ekonomik bir çelik olması nedeniyle endüstride yaygın olarak kullanılmaktadır. AISI 4140 çeliği aynı zamanda nitrürlebilen çelikler arasında yer almaktadır. Nitrürleme işlemiyle, yüzeyde elde edilen sert nitrür tabakası sayesinde sadece aşınmaya dirençli bir yüzey değil aynı zamanda yorulma dayanımında da artış sağlanmaktadır. Bu çalışmada, düşük basınçlı gaz nitrokarbürleme işlemi ve farklı sürelerde son oksidasyon işlemi uygulanmış AISI 4140 çeliğinin mikroyapısal ve yüzey özellikleri araştırılmıştır. Bu amaçla, AISI 4140 çelik numuneler, 850 °C'de 60 dk östenitlenmiş 60 °C’de yağda soğutulmuştur. Soğutma sonrası numuneler 630 °C’de 60 dk temperlenmiştir. Gaz nitrokarbürleme işlem basamakları; 350 °C’de 45 dk ön oksidasyon, 550 °C’de 90 dk nitrürleme ve 550°C’de 480 dk nitrokarbürleme uygulanmış ve ardından numuneler 45-180 dakika aralığında su buharı kullanılarak son oksidasyon işlemine tabi tutulmuştur. Mikroyapısal karakterizasyon çalışmaları optik mikroskop, tarama elektron mikroskobu (SEM), enerji dağılımlı X ışını spektrum analizi (EDX), X ışını kırınımı (XRD) analizi, mikrosertlik ve yüzey pürüzlülüğü ölçümleriyle gerçekleştirildi. X ışını analiz sonuçlarından, numunelerin yüzey katmanının demir nitrür, ɛ-Fe2-3N ve ɣ’-Fe4N fazlarını ve demir oksit (Fe3O4) içerdiği tespit edilmiştir. Son oksidasyon süresi arttıkça, demir oksit (Fe3O4) tabaka kalınlığını arttığı belirlendi. Nitrokarbürlenmiş ve son oksidasyon işlemi uygulanmış AISI 4140 çelik numuneler içerisinde, en iyi sertlik derinliği, yüzey sertliği ve yüzey pürüzlülüğü birleşimi 150 dakikada son oksidasyon uygulanmış elde edilmiştir.

Widening the operation limits of a SI engine running on neat ammonia

Present study aims to investigate the lean-burn characteristics of ammonia in a pre-mixed SI (Spark Ignition) engine and the influence of spark energy and discharge characteristics on engine performance and emissions. A wide range of engine operation conditions have been explored with particular focus on emission measurement. Engine parameters have been systematically swept to explore engine control strategies that would be operational in real engine application with a wide range of engine loads and tight emission regulations.Most previous studies required more than 5 % addition of hydrogen to the ammonia in order to achieve stable ignition for wide operation conditions. This has been a major obstacle in the application of ammonia for SI engines due to safety and system complexity issues. In present work, a comprehensive effort was made to understand and optimize the spark ignition system in order to mitigate the need for an ignition improver and all experiments have been performed with 100 % neat ammonia.With present engine modifications, emissions of unburned ammonia was measured to be between 5000 and 10000 ppm and with a combustion efficiency above 95 %. The unburned ammonia is believed to originate from crevices, particularly at the ring-pack. The NOx emission was between 4000 and 8000 ppm even at high excess air ratios. The emission of N2O is critical to minimize, as it is a strong greenhouse gas. It was measured to be between 20 and 80 ppm and appear to be related to post oxidation reactions of ammonia released from crevices during expansion.Advancing the ignition timing has proved to be an efficient handle for balancing the emissions of NH3 and NOx. These emissions will be reduced to H2O and N2 in an SCR catalyst if they are correctly balanced. Fortunately, advancing ignition timing also minimizes the formation of N2O.

Selective removal of 4H-SiC porous structures caused by photoelectric chemical etching via post oxidation annealing

Low-temperature post oxidation annealing of 4H-SiC at 900 °C for 90 min after photoelectric chemical (PEC) etching in alkaline solution can eliminate the porous structures that form during the etching process, reduce the porosity, and optimize the surface morphology, which has minimal effect on unetched surfaces, allowing for selective treatment between etched and unetched surfaces. Additionally, it can improve the etching depth and enable effective repetition of the etching process. These benefits make PEC etching a valuable technique for microstructure fabrication and surface treatment.

Femtosecond laser surface processing combined with thermal oxidation for enhancing corrosion resistance of AZ31B magnesium alloy in chloride solutions

A novel method of ultrafast femtosecond laser surface processing (FLSP) combined with the post thermal oxidation (TO) treatment was employed to improve the corrosion resistance of AZ31B magnesium (Mg) alloys. FLSP with laser powers (< 100 mW) mainly creates the nanostructures on AZ31B alloy surfaces, while the higher laser powers (> 200 mW) induce the hierarchical micro/nanostructures. According to the electrochemical results, the corrosion resistance of AZ31B alloys in Cl− solutions is weakened after the FLSP. However, an obvious enhancement in corrosion resistance is found when the femtosecond (fs) laser-processed samples subjected to the TO treatment in the temperature range from 100 °C to 280 °C. TO treatment actually supports the oxidation and growth of the nanostructure to form a dense film, considerably improving its protective ability and enhancing the corrosion resistance of Mg alloys in Cl− solutions. The uniform corrosion is evidently inhibited and localized corrosion emerges on laser-processed samples after the TO treatment.

Effect of piston bowl geometry and spray angle on engine performance and emissions in HCCI engine using multi‐stage injection strategy

AbstractThe homogeneous charge compression ignition (HCCI) and combustion chamber geometry play significant roles in improving the potential of compression ignition engines and their environmental sustainability. However, a major hindrance to the progress of HCCI technology has been the notable decline in brake thermal efficiency and emit high levels of hydrocarbon (HC) and carbon monoxide (CO) which is mainly due to the low temperatures during combustion and low post oxidation of these components. Combustion chambers like hemispherical combustion chamber (TCC) and toroidal combustion chamber (TCC) are known to provide better combustion characteristics due to their increased surface‐to‐volume ratio. Moreover, injection timing and spray position have shown a significant effect on the controlling onset of combustion and emission in HCCI engine. Therefore, the primary objective of this numerical study is to enhance the engine characteristics in HCCI mode using an HCC and TCC piston bowl geometry coupled with multistage injection and compare the results with flat piston bowl geometry. The results show that the toroidal shape piston geometry provides 3%–5% higher brake thermal efficiency compared to the conventional piston geometry. Additionally, the energy balance analysis revealed that the combination of modified piston geometry and multi stage injection improved the combustion process by reducing the energy losses due to incomplete combustion and heat transfer to the engine walls. These findings suggest that the proposed injection strategy combined with modified piston geometry has the potential to enhance the performance of HCCI engines and reduce their environmental impact.

Study of defects distribution in SiO2/SiC with plasma oxidation and post oxidation annealing

Microwave plasma oxidation is a method to realize high quality SiC gate oxide instead of thermal oxidation. In order to achieve good dielectric reliability by microwave plasma oxidation, the defects distribution in the oxide layer after post oxidation annealing (POA) have been studied. The deconvolution of X-ray photoelectron spectroscopy (XPS) spectra at different distances from the interface were analyzed to obtain the distribution of oxygen deficiency throughout the entire oxide layer. POA treatment has been confirmed to decrease oxygen deficiency. Besides, the distribution trend of oxygen vacancies near the interface by secondary ion mass spectrometry analysis is consistent with the XPS results. Considering the reaction between oxygen vacancy and oxygen atom, a kinetic model was proposed to explain the repair mechanism. This explanation is further confirmed by a series of electrical characterization, such as the leakage current density, time-dependent dielectric breakdown, the density of interface traps, border trap and fixed charge of SiO2/SiC stacks. The variation of these electrical properties with annealing temperature is consistent with the variation of oxygen vacancy with annealing temperature.

Heterogeneous CMOS Integration of InGaAs-OI nMOSFETs and Ge pMOSFETs Based on Dual-Gate Oxide Technique.

A compatible fabrication technology for integrating InGaAs nMOSFETs and Ge pMOSFETs is developed based on the development of the two-step gate oxide fabrication strategy. The direct wafer bonding method was utilized to obtain the InGaAs-Insulator-Ge structure, providing the heterogeneous channels for CMOS integration. Superior transistor characteristics were achieved by optimizing the InGaAs gate oxide with a self-cleaning process in atomic layer deposition, and modifying the Ge gate oxide by the ozone post oxidation (OPO) technique, in the sequential two-step gate oxide fabrication process. With the combination of the gate-first fabrication process, superior on- and off-state characteristics, i.e., on current up to 8.3 µA/μm and leakage as low as 10-6 µA/μm, have been demonstrated in the integrated MOSFETs, together with the preferable symmetric output characteristics that promises excellent CMOS performances.

Origin of trap assisted tunnelling in ammonia annealed SiC trench MOSFETs

The interface between silicon carbide (SiC) and silicon dioxide (SiO2) is of considerable importance for the performance and reliability of 4H-SiC (trench) metal oxide semiconductor field effect transistors (MOSFETs) and various different post oxidation anneals (POAs) have been used to optimize its quality. Whereas nitric oxide (NO) POA leads to very reliable and well performing MOSFETs, ammonia (NH3) can further improve the device performance, however, at the cost of the gate oxide (GOX) reliability, e.g. leading to trap assisted tunneling (TAT). We investigate the origin of TAT and GOX leakage in differently annealed gate oxides experimentally, using 4H-SiC trench MOSFETs, and theoretically, using Density Functional Theory (DFT) simulations. Our findings reinforce the view that the NO anneal for SiC devices results in the best overall quality as devices annealed in NH3 and nitrogen N2 show higher oxide charge density and leakage currents. DFT simulations demonstrate that, contrary to what has often been assumed so far, NH3 annealing leads to the formation of additional hydrogen related defects, which open leakage paths in the oxide otherwise not present in NO treated oxides.

Highly dense Mn3O4 and CuMn2O4 spinels as efficient protective coatings on solid oxide fuel cell interconnect and their chromium diffusion studies

In this study, we report Mn 3 O 4 and CuMn 2 O 4 spinels as potential protective coating materials on metallic solid oxide fuel cell (SOFC) interconnect SUS430 and their ability to resist chromium diffusion in intermediate temperatures. Powder x-ray diffraction and scanning electron microscopic studies confirm the formation of a single-phase spinel structure with dense microstructure. The high-temperature dc-resistivity measurements show low activation energies for both spinels and demonstrates the ability of good electrical conductivity at intermediate temperatures. The low activation energy at intermediate temperature estimated from electrical studies for both spinels confirm the compatibility of spinels to use as potential protective coating materials. Further, Mn 3 O 4 and CuMn 2 O 4 spinels are coated over ferritic stainless -steel (SUS430 grade) coupon by manual dip coating technique. The cross-section micrographs of both protective coatings show dense microstructures and better adhesion to SUS430. The oxidation kinetics studies show superior resistance to chromium diffusion and post oxidation microstructure characterizations verify the same. Finally, the impact of chromium diffusion on the electrical properties of coated coupons is undertaken by the area-specific resistance (ASR) measurements. The ASR for Mn 3 O 4 coated SUS430 is ~10 mΩ·cm 2 whereas CuMn 2 O 4 coated SUS430 shows ~15 mΩ·cm 2 after 1000 h of oxidation. • Development of spinel based protective coating as protective coating. • Dense microstructure with good adhesion over SUS430. • Better resistance for chromium diffusion at 750 °C. • Compatible ASR up to 1000 hrs oxidation cycle.

CFD analysis of combustion and emission formation using URANS and LES under large two-stroke marine engine-like conditions

In this paper, the main aim is to examine the performance of turbulence models to shed light on the effect of turbulence modeling in capturing different in-cylinder phenomena under large two-stroke marine engine-like conditions. The Unsteady Reynolds Averaged Navier–Stokes (URANS) and Large Eddy Simulation (LES) turbulence models are utilized. The LES and URANS results are compared with experimental data, in which LES and URANS models show similar accuracy in capturing the pressure and heat release with a moderately better accuracy in the LES case. The predicted gas temperature at the liner wall is approximately 45% higher for URANS than LES during the expansion stroke, which may lead to different sulfuric acid formation and heat transfer prediction. The LES model predicts a 34% higher average swirl than that in the URANS case which leads to an earlier and a stronger interaction between the flame and the spray, decreasing the oxidation of the emissions. Due to the higher predicted in-cylinder temperature in the LES case, the NO emission amount at exhaust valve opening time (EVO) is 7% higher in the LES case. At EVO, the CO emission in the LES case is predicted to be 3-fold higher than that in the URANS case due to less oxidation of CO in the post oxidation stage in the LES case. The second cycle LES simulation shows that the solutions after the scavenging process are in-sensitive to the initial conditions.

Synthesis and characterization of porous-crystalline C/Fe3O4 microspheres by spray pyrolysis with steam oxidation as anode materials for Li-ion batteries

This work introduces a novel synthesis route for the porous-crystalline C/Fe3O4 microspheres by spray pyrolysis with post oxidation under a steam atmosphere. The dense-amorphous C/Fe3O4 microspheres prepared by spray pyrolysis are firstly annealed at 700 °C for 4 h under 3 %H2/N2 atmosphere to crystallize the amorphous carbon and introduce micro- and meso-pores. The reduced Fe3C nanoparticles are then oxidized into highly-crystalline Fe3O4 at 500 °C for 2 h under H2O(g)/N2 atmosphere. The XRD, Raman, XPS, and N2 sorption analysis confirm the successful formation of C/Fe3O4 microspheres with well-developed porous structure and highly conductive graphitic carbon. The porous-crystalline C/Fe3O4 microspheres demonstrate a higher specific capacity of ∼560 mA h g−1 at a current density of 50 mA g−1 than the dense-amorphous microspheres, which corresponds to 92% of its theoretical value. Moreover, the sample has an improved rate capability (240 mA h g−1 even at 5000 mA g−1) and stable long-term cycling performance due to the synergy between porous structure and graphitic carbon.

Effects of post oxidation of SiO2/Si interfaces in ultrahigh vacuum below 450 °C

Growing SiO2 layer by wet-chemical oxidation of Si surfaces before growth of another insulating film(s) is a used method to passivate Si interfaces in applications (e.g., solar cell, photodiode) at low temperatures (LT) below 450 °C. We report on potential of LT ultrahigh-vacuum (UHV) treatments combined with the wet-chemical oxidation, by investigating effects of LT-UHV oxidation after the wet-chemical growth of SiO2 and before growing Al2O3 film on top of SiO2/Si. This method modifies the SiO2/Si and is found to (i) decrease defect-level density, (ii) increase negative fixed charge density, and (iii) increase carrier lifetime for Al2O3/SiO2/p-Si, as compared to state-of-the-art SiO2/p-Si reference interfaces without LT-UHV. X-ray photoelectron spectroscopy shows that the LT-UHV treatment decreases amount of Si+3 oxidized atoms in chemically grown SiO2 and also amount of carbon contamination. In order to pave the way for further tests of LT-UHV in silicon technology, we present a design of simple UHV instrument. The above-described benefits are reproduced for 4-inch silicon wafers by means of the instrument, which is further utilized to make LT-UHV treatments for complementary SiO2/Si interfaces of the native oxide at silicon diode sidewalls to decrease the reverse bias leakage current of the diodes.

Surface Modification of Decellularized Natural Cellulose Scaffolds with Organosilanes for Bone Tissue Regeneration.

The utility of plant tissues as scaffolding materials has been gaining significant interest in recent years owing to their unique material characteristics that are ideal for tissue regeneration. In this study, the degradation and biocompatibility of natural cellulosic scaffolds derived from Borassus flabellifer (Linn.) (BF) immature endosperm was improved by chemical oxidation and surface functionalization processes. Briefly, thus obtained cellulosic scaffolds were sequentially processed via a detergent exchange decellularization process followed by sodium periodate mediated oxidation and organosilane-based surface modification using amino (NH2)-terminated 3-aminopropyltriethoxysilane (APTES) and methyl (CH3)-terminated octadecyltrichlorosilane (OTS). Post oxidation and surface functionalization, the scaffolds showed improved physiochemical, morphological, and mechanical properties. Especially, the swelling capacity, total porosity, surface area, degradation kinetics, and mechanical behavior of scaffold were significantly higher in modified scaffold groups. The biocompatibility analysis demonstrated excellent cellular adhesion, proliferation and differentiation of osteoblasts with an evident upregulation of mineralization. Subcutaneous implantation of these scaffolds in a rat model demonstrated active angiogenesis, enhanced degradation, and excellent biocompatibility with concomitant deposition of a collagen matrix. Taken together, the native cellulosic scaffolds post chemical oxidation and surface functionalization can exclusively integrate the potential properties of native soft tissue with ameliorated in vitro and in vivo support in bone tissue engineering for nonloading bearing applications.

Reaction of nitrous oxide and ammonia molecules at 4H-SiC/SiO[formula omitted] interface: An ab initio study

The reactions of N2O and NH3 molecules at the interface between 4H-SiC and SiO2 during post oxidation annealing (POA) are theoretically investigated using ab initio calculations. We find that the reactions of N2O molecule at (0001) and (0001¯) interfaces result in the desorption of carbon oxide molecules in addition to Si–N bond formation. For the reaction of NH3 molecule, various atomic configurations are formed depending on the plane orientation. Furthermore, the energy barriers for the N2O and NH3 reactions are found to be higher than that of the NO reaction owing to different atomic configurations at the transition state structure. The calculated results shed some insights for understanding POA process at 4H-SiC/SiO2 interfaces.

Superior acetone sensor based on hetero-interface of SnSe2/SnO2 quasi core shell nanoparticles for previewing diabetes

To improve gas sensing performance of SnO2 sensor, a heterostructure constructed by SnO2 and SnSe2 is designed and synthesized via hydrothermal method and post thermal oxidation treatment. The obtained SnSe2/SnO2 composite nanoparticles demonstrate a special core–shell structure with SnO2 nanograins distributed in the shell and mixed SnSe2 and SnO2 nanograins in the core. Owning to the promoted charge transfer effect invited by SnSe2, the sensor based on SnSe2/SnO2 composite nanoparticles exhibit expressively enhanced acetone sensing performance compared to the pristine SnO2 sensor. At the working temperature of 300 °C, the SnSe2/SnO2 composite sensor with optimized composition exhibits superior sensing property towards acetone, including high response (10.77–100 ppm), low theoretical limit of detection (0.354 ppm), high selectivity and good reproducibility. Moreover, the sensor shows a satisfactory sensing performance in trace acetone gas detection under high humidity condition (relative humidity: 70–90%), making it a promising candidate to constructing exhaled breath sensors for acetone detection.

High temperature steam oxidation performance of uranium dioxide based accident tolerant fuel

Uranium dioxide (UO2) is currently the most widely used nuclear fuel for commercial nuclear reactors. However, the Fukushima Daiichi nuclear disaster revealed the primary safety risks of this kind of fuel under accident conditions, which thereby stimulated various international programs in developing accident tolerant fuel (ATF). Silicon carbide (SiC) and Zirconium (Zr) are being introduced as additives to enhance thermal properties and fission product retention ability of the UO2 single crystals (SCs) pellet. The oxidation resistance in water at high temperatures is essential to the deployment of ATF. In this work, two kinds of enhanced UO2 single crystal pellets by using SiC and Zr particles as additives (denoted as UO2 SCs-SiC and UO2 SCs-Zr, respectively) were fabricated through spark plasma sintering (SPS) processes. The impact of steam oxidation on UO2 SCs-SiC and UO2 SCs-Zr was investigated through the microstructures, phase compositions and post oxidation performances characterizations. The results revealed that the pellets with SiC as additives showed good oxidation resistance in water even at 1200 °C while that with Zr as additives showed complete oxidization which resulted in the formation ZrO2 powder.

Extensive jarosite deposits formed through auto-combustion and weathering of pyritiferous mudstone, Smoking Hills (Ingniryuat), Northwest Territories, Canadian Arctic – A potential Mars analogue

Jarosite and other metal sulphates are common on Mars and are interpreted to have formed in an extreme acidic saline aqueous environment, similar to modern Earth analogues where jarosite precipitates. We examined an alternative Earth analogue, at the Smoking Hills (known as Ingniryuat by Inuvialuit), Northwest Territories, Arctic Canada. The Smoking Hills are characterised by auto-combusting pyritic mudstones of the Smoking Hills Formation in a polar desert. The Smoking Hills Formation was deposited in an outer shelf to slope marine environment, during a Late Cretaceous Ocean Anoxic Event. Oxidative weathering of this unit creates extensive jarosite-rich deposits, and banded jarosite- and phyllosilicate-rich mudstones, similar to those observed on Mars. Slumping of these mudstones exposes large masses to atmospheric oxygen leading to generation of high temperatures (sufficient to produce paralavas) through pyrite oxidation, and the subsequent formation of a diverse suite of hydrated metal-sulphate minerals. Weathered combustion sites are characterised by a simpler jarosite-rich mineralogy along with thermally-altered mudstone. Away from sites of auto-combustion (bocannes), pyrite-rich layers within the mudstone oxidise to jarosite, creating a yellow-banded appearance in outcrops. These jarosite-rich layers, similar to those observed interbedded in mudstones on Mars, reflect post depositional oxidation processes - not acidic conditions during the time of deposition. As such, this could reflect a more habitable environment than is commonly interpreted for Mars.