C.R. Pichard

Bio: C.R. Pichard is an academic researcher. The author has contributed to research in topics: Electrical resistivity and conductivity & Hall effect. The author has an hindex of 9, co-authored 12 publications receiving 239 citations.

A three-dimensional model for grain boundary resistivity in metal films

Abstract: In this work a model is proposed to express the resistivity of metal films in which two electron scattering mechanisms operate simultaneously: an isotropic background scattering and a scattering caused by three distributions of planar potentials which represent the grain boundaries. In order to describe the average properties of grain boundaries a transmission coefficient t is introduced. An interpretation of published fine-grained film data in terms of the three-dimensional model yields reasonable values of t .

Thermoelectric power of thin polycrystalline metal films in an effective mean free path model

Abstract: Starting from an effective Fuchs-Sondheimer conduction model, the theoretical expression for the thermoelectric power of polycrystalline metal films is derived. From the approximate expression for thick films, a procedure is proposed to determine the variation in the electronic mean free path.

Thermal strains in thin metallic films

Abstract: Theoretical formulations of strain coefficient of resistance and resistivity in supported and unsupported thin metallic films are examined. The case of thermal strains is emphasised and an expression of the difference in TCR of supported and unsupported films is derived.

Experimental determination of electronic transport parameters in monocrystalline metallic films

Abstract: New equations for the resistivity and temperature coefficient of resistivity (TCR) of monocrystalline films are derived from the theoretical predictions of the two-dimensional model previously proposed to describe the simultaneous scatterings due to the background, external surfaces and grain boundaries. It is found that the dependences of the film resistivity p Fm and TCR β Fm on the thickness a when they are plotted in the forms a p Fm and a β Fm -1 versus a should yield straight lines with slopes of p 0 and β 0 -1 respectively and an identical intercept on the ordinate of M ( t,p ). An analytical expression for M ( t,p ) as a function of the transmission coefficient t and the specularity parameter p is obtained which allows a systematic study of the changes in these parameters under various annealing and deposition conditions.

Decomposition of polycrystalline metallic film resistivity from Mathiessen's rule

Abstract: Using the framework of the Mayadas-Shatzkes and the effective Fuchs-Sondheimer conduction models an approximate relation for the product of the film resistivity with its TCR is obtained. As a consequence, the film resistivity may be represented by the sum of the bulk resistivity and an additional resistivity which is temperature-independent.

Interconnect limits on gigascale integration (GSI) in the 21st century

Abstract: Twenty-first century opportunities for GSI will be governed in part by a hierarchy of physical limits on interconnects whose levels are codified as fundamental, material, device, circuit, and system. Fundamental limits are derived from the basic axioms of electromagnetic, communication, and thermodynamic theories, which immutably restrict interconnect performance, energy dissipation, and noise reduction. At the material level, the conductor resistivity increases substantially in sub-50-nm technology due to scattering mechanisms that are controlled by quantum mechanical phenomena and structural/morphological effects. At the device and circuit level, interconnect scaling significantly increases interconnect crosstalk and latency. Reverse scaling of global interconnects causes inductance to influence on-chip interconnect transients such that even with ideal return paths, mutual inductance increases crosstalk by up to 60% over that predicted by conventional RC models. At the system level, the number of metal levels explodes for highly connected 2-D logic megacells that double in size every two years such that by 2014 the number is significantly larger than ITRS projections. This result emphasizes that changes in design, technology, and architecture are needed to cope with the onslaught of wiring demands. One potential solution is 3-D integration of transistors, which is expected to significantly improve interconnect performance. Increasing the number of active layers, including the use of separate layers for repeaters, and optimizing the wiring network, yields an improvement in interconnect performance of up to 145% at the 50-nm node.

Size‐Dependent Transport and Thermoelectric Properties of Individual Polycrystalline Bismuth Nanowires

Abstract: Thermoelectric materials convert a temperature difference into electricity and vice versa. [1–3] Such materials utilize the Seebeck effect for power generation and the Peltier effect for cooling. In the Seebeck effect, a temperature difference across a material causes the diffusion of charged carriers across that gradient, thus creating a voltage difference between the hot and cold ends of the material. Conversely, the Peltier effect explains the fact that when current flows through a material a temperature gradient arises because the charged carriers exchange thermal energy. Thermoelectrics perform these functions without moving parts or toxic gases, which make them unique among power generation and cooling methods. Presently, thermoelectrics find only limited use because of their poor efficiency. The efficiency of a thermoelectric material is determined by the dimensionless figure of merit

The experimental investigation of thermal conductivity and the Wiedemann-Franz law for single metallic nanowires

Abstract: A new method for the measurement of thermal conductivity of electrically conducting single nanowires is presented. First experimental investigations are focused on the thermal conductivity of metallic Pt nanowires with a diameter of (typically) 100 nm and a length of 10 µm. Thermal conductivity data are compared with measurements of electrical conductivity in order to test the Wiedemann–Franz law for metallic nanowires. Compared to the bulk values at room temperature, electrical and thermal conductivities of the nanowire are decreased by a factor of 2.5 and 3.4, respectively. Consequently, the Lorenz number L = λ/σT = 1.82 × 10−8 V2 K−2 of the nanowire is smaller than the bulk Lorenz number Lbulk = (π2/3)(k/e)2 = 2.44 × 10−8 V2 K−2 of metals. Furthermore, the temperature coefficient β of electrical resistivity is also reduced compared to the bulk value. These decreases of λ, σ and β can be attributed to size effects, mainly caused by grain boundary scattering of electrons.

The resistivity of thin metal films—Some critical remarks

Abstract: This article highlights the problems associated with interpreting data on the resistivity of thin films. It is pointed out that extreme care must be taken in analysing data and a thorough study should be made of the morphology of the films from which data are taken. Without this, values deduced for parameters such as the surface roughness, the specularity and in particular the product of the bulk resistivity and the bulk mean free path are worthless. Even when the scattering contributions from the surface and the grain boundaries are taken properly into account, because of the high defect and dislocation densities in many of the films studied the values deduced for these parameters are still in doubt.

Thermoelectric power of thin polycrystalline metal films in an effective mean free path model

Abstract: Starting from an effective Fuchs-Sondheimer conduction model, the theoretical expression for the thermoelectric power of polycrystalline metal films is derived. From the approximate expression for thick films, a procedure is proposed to determine the variation in the electronic mean free path.