There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

An introduction to heat transfer

International Technology Roadmap for Semiconductors 2003の要求清浄度について － シリコンウエハ表面と雰囲気環境に要求される清浄度, 分析方法の現状について －

The stability of two-dimensional (2D) layers and membranes is subject of a long standing theoretical debate. According to the so called Mermin-Wagner theorem, long wavelength fluctuations destroy the long-range order for 2D crystals. Similarly, 2D membranes embedded in a 3D space have a tendency to be crumpled. These dangerous fluctuations can, however, be suppressed by anharmonic coupling between bending and stretching modes making that a two-dimensional membrane can exist but should present strong height fluctuations. The discovery of graphene, the first truly 2D crystal and the recent experimental observation of ripples in freely hanging graphene makes these issues especially important. Beside the academic interest, understanding the mechanisms of stability of graphene is crucial for understanding electronic transport in this material that is attracting so much interest for its unusual Dirac spectrum and electronic properties. Here we address the nature of these height fluctuations by means of straightforward atomistic Monte Carlo simulations based on a very accurate many-body interatomic potential for carbon. We find that ripples spontaneously appear due to thermal fluctuations with a size distribution peaked around 70 \AA which is compatible with experimental findings (50-100 \AA) but not with the current understanding of stability of flexible membranes. This unexpected result seems to be due to the multiplicity of chemical bonding in carbon.

Intrinsic ripples in graphene

Magnetocaloric effect: From materials research to refrigeration devices

Based on the charge analysis in the Pao-Sah model assuming the exponential deep and tail density of trap states (DOS), the above-threshold current expressions are presented. The trapped charge in the deep DOS is included in the threshold voltage. In particular, a trapped charge effect parameter β, which is determined mainly by the tail DOS, is introduced into the current expressions. The parameter clarifies the relationship between the free electrons and the trapped electrons concentration, and shows the relationship between the band mobility μ
 b
 and the constant effective mobility μ
 con
. The expressions are consistent with the Pao-Sah model and verified by the experimental data. The different effects of the deep and tail DOS are clarified.

Trapped-Charge-Effect-Based Above-Threshold Current Expressions for Amorphous Silicon TFTs Consistent With Pao–Sah Model

The linear cofactor difference extrema due to the nonlinearity of the MOSFET drain-current and their application to extract MOSFET parameters are presented in this brief. The extrema of drain-current are obtained by applying the linear cofactor difference operator to the drain-current versus gate voltage curve in the linear region. These extrema are directly used to find the threshold voltage and the mobility of a MOSFET. This method has been tested using data from experimentally fabricated MOSFETs and by simulating results through the device simulator DESSIS-ISE. The results agree well with those obtained by the standard second-derivative approach, which demonstrates the validity of the method presented. The advantages and disadvantages of this method are also discussed

Linear Cofactor Difference Extrema of MOSFET's Drain–Current and Application to Parameter Extraction

A semi-empirical analytical method called as the equivalent junction transformation has been proposed in this paper for the first time, and used to predict the breakdown characteristics of curved-abrupt P–N junctions. Based on this method, the effects of the radius of curvature of the metallurgical junction and the background doping concentration on the breakdown voltage, peak electrical field and depletion layer width at breakdown for cylindrical- and spherical-abrupt junctions are discussed in detail. All analytical results have shown in excellent agreement with the numerical analysis, showing the validity of the method presented here.

Equivalent junction transformation: a semi-empirical analytical method for predicting the breakdown characteristics of cylindrical- and spherical-abrupt P–N junctions

An analytic surface potential-based non-charge-sheet core model for intrinsic nanowire surrounding-gate (SRG) MOSFETs is presented in this paper. Starting from the Poisson–Boltzmann equation in the cylindrical SRG MOSFETs, a surface potential equation is derived. Based on the exact surface potential solutions evaluated at the source and drain ends, a single set of the analytic drain current expression is obtained from the Pao–Sah's dual integral without the charge-sheet approximation. The analytical trans-capacitance model is also obtained from Ward–Dutton's charge partition method within the surface potential-based model framework. It is shown that the proposed drain current model and trans-capacitance model are valid for all operation regions, allowing the nanowire SRG MOSFET characteristics to be adequately described from the linear to saturation and from the sub-threshold to strong inversion region without any fitting-parameters. Moreover, the model prediction is verified by the three-dimensional nume...

A complete analytic surface potential-based core model for intrinsic nanowire surrounding-gate MOSFETs

Based on artificial neural network (ANN), a new method of modeling carbon nanotube field effect transistors (CNTFETs) is developed. This paper presents two ANN CNTFET models, including P-type CNTFET (PCNTFET) and N-type CNTFET (NCNTFET). In order to describe the devices more accurately, a segmentation voltage of the voltage between gate and source is defined for each type of CNTFET to segment the workspace of CNTFET. With the smooth connection by a quasi-Fermi function for, the two segmented networks of CNTFET are integrated into a whole device model and implemented by Verilog-A. To validate the ANN CNTFET models, quantitative test with different device intrinsic parameters are done. Furthermore, a complementary CNTFET inverter is designed using these NCNTFET and PCNTFET ANN models. The performances of the inverter show that our models are both efficient and accurate for simulation of nanometer scale circuits.

Jin He

Papers

Trapped-Charge-Effect-Based Above-Threshold Current Expressions for Amorphous Silicon TFTs Consistent With Pao–Sah Model

Linear Cofactor Difference Extrema of MOSFET's Drain–Current and Application to Parameter Extraction

Equivalent junction transformation: a semi-empirical analytical method for predicting the breakdown characteristics of cylindrical- and spherical-abrupt P–N junctions

A complete analytic surface potential-based core model for intrinsic nanowire surrounding-gate MOSFETs

Artificial Neural Network Based CNTFETs Modeling