Optimization of KOH etching process to obtain textured substrates suitable for heterojunction solar cells fabricated by HWCVD

In this work, we have studied the texturization process of (100) c-Si wafers using a low concentration potassium hydroxide solution in order to obtain good quality textured wafers. The optimization of the etching conditions have led to random but uniform pyramidal structures with good optical properties. Then, symmetric heterojunctions were deposited by Hot-Wire CVD onto these substrates and the Quasi-Steady-State PhotoConductance technique was used to measure passivation quality. Little degradation in the effective lifetime and implicit open circuit voltage of these devices (< 20 mV) was observed in all cases. It is especially remarkable that for big uniform pyramids, the open-circuit voltage is comparable to the values obtained on flat substrates

Evidence for an ¹⁸O-depleted mantle plume from contrasting ¹⁸O/¹⁶O ratios of back-arc lavas from the Manus Basin and Mariana Trough.

no abstrac

Nucleogenic neon in high ³He/⁴He lavas from the Manus back-arc basin: a new perspective on He-Ne decoupling.

no abstract provided

High ³He/⁴He ratios in the Manus Back-Arc Basin: implications for mantle mixing and the origin of plumes in the western Pacific Ocean.Basin.

no abstrac

Genesis of the Western Samoa seamount province: age, geochemical fingerprint and tectonics

The Samoan volcanic lineament has many features that are consistent with a plume-driven hotspot model, including the currently active submarine volcano Vailulu'u that anchors the eastern extremity. Proximity to the northern end of the Tonga trench, and the presence of voluminous young volcanism on what should be the oldest (∼5 my) western island (Savai'i) has induced controversy regarding a simple plume/hotspot model. In an effort to further constrain this debate, we have carried out geochronological, geochemical and isotopic studies of dredge basalts from four seamounts and submarine banks that extend the Samoan lineament 1300 km further west from Savai'i. 40Ar/39Ar plateau ages from Combe and Alexa Banks (11.1 my—940 km, and 23.4 my—1690 km from Vailulu'u, respectively) fit a Pacific age progression very well. The oldest volcanism (9.8 my) on Lalla Rookh (725 km from Vailulu'u) also fits this age progression, but a new age is much younger (1.6 my). Isotopically, these three seamounts, along with Pasco Bank (590 km from Vailulu'u), all lie within, or closely along extensions of, the Sr–Nd–Pb fields for shield basalts from the Eastern Samoan Province (Savai'i to Vailulu'u); this clearly establishes a Samoan pedigree for this western extension of the Samoan hotspot chain, and pushes the inception of Samoan volcanism back to at least 23 my. From geodetic reconstructions of the Fiji–Tonga–Samoa region, we show that the northern terminus of the Tonga arc was too far west of the Samoa hotspot up until 1–2 my ago to have been a factor in its volcanism. Young rejuvenated volcanism on Lalla Rookh and Savai'i may be related to the rapid eastward encroachment of the Trench corner. The Vitiaz Lineament, previously thought to mark a proto-Tongan subduction zone, was more likely created by the eastward propagation of the tear in the Pacific Plate at the northern end of the arc

Investigation of geothermal potential in the Waianae Caldera Area, Western Oahu, Hawaii. Assessment of Geothermal Resources in Hawaii: Number 2

Studies of Lualualei Valley, Oahu have been conducted to determine whether a thermal anomaly exists in the area and, if so, to identify sites at which subsurface techniques should be utilized to characterize the resource. Geologic mapping identifies several caldera and rift zone structures in the Valley and provides a tentative outline of their boundaries. Clay mineralogy studies indicate that minor geothermal alteration of near-surface rocks has occurred at some period in the history of the area. Schlumberger resistivity soundings indicate the presence of a low resistivity layer beneath the valley floor, which has been tentatively attributed to warm water-saturated basalt. Soil and groundwater chemistry studies outline several geochemical anomalies around the perimeter and within the inferred caldera boundaries. The observed anomalies strongly suggest a subsurface heat source. Recommendations for further exploratory work to confirm the presence of a geothermal reservoir include more intensive surveys in a few selected areas of the valley as well as the drilling of at least three shallow (1000-m) holes for subsurface geochemical, geological and geophysical studies

L'énergie et la Chine

Ouvrage coordonné par Jean-Frnaçois Huchet et Françoise Lemoin