Influence Of Line Edge Roughness Research Articles

Line Edge Roughness Effects on the Thermoelectric Properties of Armchair Black Phosphorene Nanoribbons

AbstractThis study delves into the thermoelectric properties of armchair black phosphorene nanoribbons while considering the presence of line edge roughness. Employing the tight‐binding method in conjunction with non‐equilibrium Green's function techniques and Landauer formulas, the impact of various parameters on thermoelectric performance is explored. These findings reveal that the electrical conductivity and, consequently, the power factor exhibits an increasing trend with expanding ribbon length and width. This behavior can be attributed to heightened collision rates, particularly in narrow ribbons, induced by line edge roughness as length increases. Remarkably, the Seebeck coefficient at the Fermi energy corresponding to the maximum power factor remains nearly constant across different widths, lengths, temperatures, and transport regimes. Furthermore, the thermoelectric figure of merit (ZT) demonstrates a positive correlation with both ribbon length and width. In narrow widths and lengths ≈1000 nm, the power factor and figure of merit exhibit an upward trend with ribbon width. However, with further increases in ribbon width, the influence of line edge roughness on thermal conductivity diminishes. Consequently, the figure of merit decreases due to the rise in thermal conductivity. Notably, the thermoelectric figure of merit is higher for short and narrow ribbons and long and wider ribbons.

γ-Graphyne rectifier and NDR tunable by doping, line edge roughness and twist

The armchair γ-graphyne nanoribbon (A-γ-GyNR) based on doping boron and nitrogen atoms in left and right leads, respectively, was proposed as the initial sample of a rectifier device. Afterwards, the next five devices were presented by applying line edge roughness (LER) defect, increasing its roughness, doping concentration, and its position and twisting under six different angles to the center of the initial model. Also, the effect of width was investigated. The computational method for investigating the electronic transfer properties was a combination of the non-equilibrium Green’s function (NEGF) and the tight binding method. The current curve and transmission spectrum revealed the negative differential resistance (NDR) behavior, which underwent the most changes under the influence of LER. Density of state (DOS) peaks indicated that p-orbital had a more significant effect on transmission in all devices; on the other hand, the localization of molecular projected self-consistent Hamiltonian (MPSH) structure in positive biases resulted from the suppression of electron tunneling. Based on the findings, the maximum rectification ratio in the M″3 device, twisted by an angle of 75°, was equal to 5.86 × 108, which was 41.2 times higher than that of the initial sample; the highest NDR value of the M′1 device was 56.

Effective–CD: a contribution toward the consideration of line edge roughness in the scatterometric critical dimension metrology

We present an overview of our research on the relation between line edge roughness (LER) and optical critical dimension metrology (OCD). Referring to a known fact that LER does have an impact on OCD, we discuss a novel approach that allows for its better understanding. Namely, we show that, in the presence of LER, one can observe a characteristic scatterometry-measured CD offset, which we call effective–CD. The fact that the effective–CD is characteristic renders it to be a good means of accessing the information about LER present on the CD. To assure the completeness of this overview, we begin by reviewing some previously published results, which have drawn our attention and first led us to observing the characteristic influence of LER on a CD measurement. Next, we extend our model-based simulations to confirm the presence of the effective–CD for complex-roughness models, and finally, we demonstrate an experimental verification of our effective–CD hypothesis. We are convinced that our approach will help to better understand the impact of LER on a CD measurement and will be considered a useful contribution to the development of measurement methods for challenging scenarios, in which realistic CD is affected by the presence of LER.

Influence of line-edge roughness on multiple-gate tunnel field-effect transistors

The influence of fin-line-edge roughness (fin-LER) and gate-LER on multiple-gate (MG) tunnel field-effect transistors (TFETs) has been investigated compared with MG MOSFETs by using full three-dimensional technology computer-aided design (TCAD) simulation. From simulation results, two interesting results have been observed. First, MG TFETs show much less severe gate-LER than MG MOSFETs, which means that only fin-LER can be considered when evaluating the total LER of MG TFETs. Second, TFETs show ∼3× more LER improvement than MOSFETs when their structures are changed from double-gate (DG) to triple-gate (TG) ones. Our findings provide the useful design guidelines of variation-tolerant TFETs.

On the channel width-dependence of the thermal conductivity in ultra-narrow graphene nanoribbons

The thermal conductivity of low-dimensional materials and graphene nanoribbons, in particular, is limited by the strength of line-edge-roughness scattering. One way to characterize the roughness strength is the dependency of the thermal conductivity on the channel's width in the form Wβ. Although in the case of electronic transport, this dependency is very well studied, resulting in W6 for nanowires and quantum wells and W4 for nanoribbons, in the case of phonon transport it is not yet clear what this dependence is. In this work, using lattice dynamics and Non-Equilibrium Green's Function simulations, we examine the width dependence of the thermal conductivity of ultra-narrow graphene nanoribbons under the influence of line edge-roughness. We show that the exponent β is in fact not a single well-defined number, but it is different for different parts of the phonon spectrum depending on whether phonon transport is ballistic, diffusive, or localized. The exponent β takes values β < 1 for semi-ballistic phonon transport, values β ≫ 1 for sub-diffusive or localized phonons, and β = 1 only in the case where the transport is diffusive. The overall Wβ dependence of the thermal conductivity is determined by the width-dependence of the dominant phonon modes (usually the acoustic ones). We show that due to the long phonon mean-free-paths, the width-dependence of thermal conductivity becomes a channel length dependent property, because the channel length determines whether transport is ballistic, diffusive, or localized.

About the influence of Line Edge Roughness on measured effective–CD

Various reports state that Line Edge/Width Roughness (LER/LWR) has a significant impact on the integrated circuits fabricated by means of lithography, hence there is a need to determine the LER in-line so that it never exceeds certain specified limits. In our work we deal with the challenge of measuring LER on 50 nm resist gratings using scatterometry. We show by simulation that there is a difference between LER and no-LER scatter signatures which first: depends on the polarization and second: is proportional to the amount of LER. Moreover, we show that the mentioned difference is very specific, that is - a grating with LER acts like a grating without LER but showing another width (CD, Critical Dimension), which we refer-to as effective-CD.

Monte Carlo simulation study of scanning electron microscopy images of rough surfaces

In this paper, we have developed a Monte Carlo (MC) simulation method for calculation of scanning electron microscopy (SEM) images of rough surfaces. The roughness structure is constructed in a finite element triangulated mesh by using a Gaussian function to describe the distribution of amplitude of the random rough peaks. Further spatial subdividing can accelerate the calculation and improves MC simulation efficiency. The MC model is based on the using of the Mott cross section for description of the electron elastic scattering and the using of the full Penn algorithm in a dielectric functional approach to the electron inelastic scattering. This simulation relates directly a defined rough surface structure modeling described by exact values of roughness parameters to the contrast observed in a SEM image, enabling the investigation of the influence of line edge roughness to the critical dimension (CD) metrology of a metal-oxide-semiconductor device by SEM. Example calculation of line images with sidewall roughness demonstrates that the present MC simulation method is useful for CD metrology of nanostructures by CD-SEM and, especially, for the linewidth measurement in the integrated circuit industry.