Large Area CoNi Stress Free Electroformed Mold for Nanoimprint Lithography

Nanoimprint lithography is a novel method of fabricating nanometer scale patterns. It is a simple process with low cost, high throughput and high resolution. But it also requires a stamp which has a lower fabrication cost and longer life time. Depending on application, stamps in wafer-size scale have been studied by several groups. CoNi alloys can be used to fabricate a nano-size patterned mold by electrodeposition on a Si mother mold with a seed layer. After electrodeposition, the sample is usually dipped in KOH solution to remove Si. The consumption of Si mold is a necessary step to produce a stamp. In this study, a method was developed to fabricate CoNi alloy stamps without the consumption of Si mother mold. Vapor self assembled monolayer (SAM) method was used to deposit an anti-adhesion layer instead of Si removal method. SAM has a low surface energy, makes possible to separate Ni from Si substrate without causing any damages on Si mold. Especially, vapor SAM method has its advantage when the mold features are in nanometer scale. It eliminates the use of organic solvents and greatly simplifies the handling of the sample. As a result, 140mm CoNi stamp for NIL has been successfully fabricated from a nano Si mother mold by using a developed method. The characteristics of deposited SAM were analyzed by measurements of the contact angle, its hysteresis, surface energy, thickness and lateral friction force. Duplicated patterns on CoNi alloy stamp were compared with those of Si mother mold by using field emission scanning electron microscopy (FE-SEM) and atomic force microscopy (AFM). This process enables us to produce a cost effective metal nano stamp

Transient radiative transfer in participating media with pulse-laser irradiation - an approximate Galerkin solution

An assessment is made of the Galerkin technique as an effective method of solution for transient radiative transfer problems in participating media. A one-dimensional absorbing and isotropically scattering plane-parallel gray medium irradiated with a short-pulse laser on one of its boundaries is considered for the application of the method. The medium is non-emitting and the boundaries are non-reflecting and non-refracting. In the integral formulation of the problem for the source function, the time-wise variation of the radiation intensity at any point and in any direction in the medium is assumed to be the same as the time-wise variation of the average intensity at the same point as an approximation for the application of the method. The transient transmittance and reflectance of the medium are evaluated for various values of the optical thickness, scattering albedo and pulse duration. The results are in agreement with those available in the literature. It is demonstrated that the method is relatively simple to implement and yields accurate results