An introduction to heat transfer

One of the most frequently used methods for characterizing thin films is UV–Vis absorption. The near-edge region can be fitted to a simple expression in which the intercept gives the band-gap and the fitting exponent identifies the electronic transition as direct or indirect (see Tauc et al., Phys. Status Solidi 15, 627 (1966); these are often called “Tauc” plots). While the technique is powerful and simple, the accuracy of the fitted band-gap result is seldom stated or known. We tackle this question by refitting a large number of Tauc plots from the literature and look for trends. Nominally pure zinc oxide (ZnO) was chosen as a material with limited intrinsic deviation from stoichiometry and which has been widely studied. Our examination of the band gap values and their distribution leads to a discussion of some experimental factors that can bias the data and lead to either smaller or larger apparent values than would be expected. Finally, an easily evaluated figure-of-merit is defined that may help guide more accurate Tauc fitting. For samples with relatively sharper Tauc plot shapes, the population yields Eg(ZnO) as 3.276 ± 0.033 eV, in good agreement with data for single crystalline material.

Evaluation of the Tauc method for optical absorption edge determination: ZnO thin films as a model system

In the past decade graphene has been one of the most studied material for several unique and excellent properties. Due to its two dimensional nature, physical and chemical properties and ease of manipulation, graphene offers the possibility of integration with the exiting semiconductor technology for next-generation electronic and sensing devices. In this context, the understanding of the graphene/semiconductor interface is of great importance since it can constitute a versatile standalone device as well as the building-block of more advanced electronic systems. Since graphene was brought to the attention of the scientific community in 2004, the device research has been focused on the more complex graphene transistors, while the graphene/semiconductor junction, despite its importance, has started to be the subject of systematic investigation only recently. As a result, a thorough understanding of the physics and the potentialities of this device is still missing. The studies of the past few years have demonstrated that graphene can form junctions with 3D or 2D semiconducting materials which have rectifying characteristics and behave as excellent Schottky diodes. The main novelty of these devices is the tunable Schottky barrier height, a feature which makes the graphene/semiconductor junction a great platform for the study of interface transport mechanisms as well as for applications in photo-detection, high-speed communications, solar cells, chemical and biological sensing, etc. In this paper, we review the state-of-the art of the research on graphene/semiconductor junctions, the attempts towards a modeling and the most promising applications.

Graphene Schottky diodes: an experimental review of the rectifying graphene/semiconductor heterojunction

A novel fault diagnosis technique for photovoltaic systems based on artificial neural networks

Graphene Schottky diodes: An experimental review of the rectifying graphene/semiconductor heterojunction

Induced degradation on c-Si solar cells for concentration terrestrial applications

In this paper the hardware implementation of a PV microinverter based on dual coupled-inductors dc-dc converters is presented. Coupled-inductors were sized to ensure a high coupling factor, as well as to reach the desiderate voltage gain. Moreover, wide Band-Gap devices allowed to reduce weight and volume of the overall system. The control technique was optimized by adding a PI regulator to a sliding mode controller. Preliminary experimental tests are shown to demonstrate that the circuit is fully-functional and that the design approach was well-conceived.

A single panel PV microinverter based on coupled inductor DC-DC

SiC MOSFETs have already replaced silicon-based device in power applications, even if some technological issues are still not solved. Among others, the complex traps distribution at SiC/SiO2 interface is of foremost importance. Interface traps affect the overall device behavior, modifying channel mobility and introducing hysteresis. In this work, the capacitance behavior, when the Drain terminal is floating, is studied through numerical analysis. The effects of traps distribution and its properties on such curves has been studied along with temperature effects. Experimental curves are carried out at various temperatures and compared to the same trends of numerical results.

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SiC MOSFET C-V Curves Analysis with Floating Drain Configuration

Modelling of the Input Characteristics of Bipolar JFET Structures

The operation of micro-optoelectronic devices relies on optical properties of materials, first of all the wavelength dependent refractive index. Standard measurement techniques are often prone to significant ambiguities caused by the periodic nature of the optical response. In this paper we propose a procedure which exploits transmittance measurements, performed at variable light incidence angle, to reconstruct the complex refractive index as a function of the wavelength. Experiments performed on a thin TCO layer prove the reliability of the method.

Santolo Daliento

Papers

Induced degradation on c-Si solar cells for concentration terrestrial applications

A single panel PV microinverter based on coupled inductor DC-DC

SiC MOSFET C-V Curves Analysis with Floating Drain Configuration

Modelling of the Input Characteristics of Bipolar JFET Structures

Refractive index measurement in TCO layers for micro optoelectronic devices