An innovative rear contacting structure for copper indium gallium (di) selenide (CIGS) thin-film solar cells is developed in an industrially viable way and demonstrated in tangible devices. The idea stems from the silicon (Si) industry, where rear surface passivation layers are combined with micron-sized local point contacts to boost the open-circuit voltage (V O C ) and, hence, cell efficiency. However, compared with Si solar cells, CIGS solar cell minority carrier diffusion lengths are several orders lower in magnitude. Therefore, the proposed CIGS cell design reduces rear surface recombination by combining a rear surface passivation layer and nanosized local point contacts. Atomic layer deposition of Al 2 O 3 is used to passivate the CIGS surface and the formation of nanosphere-shaped precipitates in chemical bath deposition of CdS to generate nanosized point contact openings. The manufactured Al 2 O 3 rear surface passivated CIGS solar cells with nanosized local rear point contacts show a significant improvement in V O C compared with unpassivated reference cells. Index Terms-Al 2 O 3 , atomic layer deposition, copper indium gallium selenide (CIGS), Cu(In,Ga)Se 2 , Ga grading, nanosized, passivated emitter, passivated emitter and rear cell (PERC), photovoltaics, point contact openings rear locally diffused cell (PERL), rear surface passivation, Si, solar cells, thin film.

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This article demonstrates that micro-Raman spectroscopy is a very powerful technique for the study of a variety of problems related to metal salicides for Si device fabrication. In addition to its versatile nature and ease of use, this technique provides some unique capabilities that complement the commonly used tools for Si device characterization. Phase identification of the TiSi2 C54, C49, and C40 phases as well as NiSi and NiSi2 can be achieved easily using Raman spectroscopy. The phase transition process from NiSi to NiSi2 has also been successfully monitored. Raman band assignments for C40 TiSi2 and NiSi are also made in order to have a better understanding of the Raman spectra. Thickness measurement of ultrathin salicide films from 45 nm down to 6 nm has been accurately performed using attenuation of the Si Raman signal at 520 cm−1, and film uniformity can also be evaluated using the same peak. Local orientations of the NiSi grains are studied by the relative intensity of the NiSi Raman peaks with micron spatial resolution, which provides complementary information to the space-averaged x-ray diffraction result.

The unique electronic properties of graphene are exploited for field-effect sensing in both capacitor and transistor modes when operating the sensor device in electrolyte. The device is fabricated using large-area graphene thin films prepared by means of layer-by-layer stacking. Although essentially the same device, its operation in the capacitor mode is found to yield more information than in the transistor mode. The capacitor sensor can simultaneously detect the variations of surface potential and electrical-double-layer capacitance at the graphene/electrolyte interface when altering the ion concentration. The capacitor-mode operation further facilitates studies of the molecular binding-adsorption kinetics by monitoring the capacitance transient.