Introduction. 4Theory and technology of xxxxxx. 5 2.1. Nanospectrometer 5 2.1.1. Distributed Bragg reflector (DBR) 5 2.1.2. Fabry-P?rot Filter 7 2.2. Nanoimprint lithography. 9 2.3. Technique of Master template fabrication. 11 2.3.1. Optical lithography. 11 2.3.2. Reactive ion etching (RIE) 13 2.4. White light interferometer (WLI) 15 1. Introduction Please write a short introduction (3 pages). These are just few suggestions: Introduce nanimprint lithography vs optical lithography What are advantages of nanoimprint Master template as an important component Many latest literature review. 2.1. Nanospectrometer Please write 2 pages on nanospectrometer 2.1.1. Distributed Bragg reflector (DBR) Distributed Bragg reflector (DBR) is a high reflectivity mirror that reflects light in a certain wavelength region called stop-band. The Bragg reflector consists of a sequence of deposited layers of high and low refractive indices materials. To reflect a particular wavelength range, the optical thickness of each layer has to be ª of the central wavelength. When light passes through the DBR, a complex interference phenomenon takes place through these multiple layers. The schematic diagram of a DBR is shown in Figure 2 ?1 and its spectrum is shown in Figure 2 ?2. Figure 2 ?1: A schematic of Distributed Bragg Reflector (DBR). Ref: Based on H. A. Macleod: Thin-Film Optical Filters 3rd edition, Inst. of Physics Publ., 2001. Where is the central wavelength, d is the physical thickness and n is the refractive index. Figure 2 ?2: Simulated spectrum of a DBR. A bit more theory on DBR could be included and extended. Interference Stop band Reflectance formula 2.1.2. Fabry-P?rot Filter Fabry-P?rot (FP) filter consists of two distributed Bragg reflectors which are separated by a certain length called a cavity length. The thickness of each layer and the cavity length define the transmitted wavelength through the FP-filter while the other wavelengths are filtered out. A schematic diagram of the FP-filter structure is shown in Figure 2 ?3 and an example spectrum of the FP-filter is shown in Figure 2 ?4. Figure 2 ?3: Schematic Structure of Fabry P?rot filter. Ref: Prof. Hillmer: Optoelectronic devices manuscript Figure 2 ?4: Simulation results for FP Filter with 550 nm reference wavelength. Simple FP-filter theory could be extended e.g. Formula. Tuning of dip 2.2 Nanoimprint lithography Simple theory of nanoimprint lithography to be extended briefly (2 pages). A principle process flow of the UV nanoimprint lithography is illustrated in Figure 2 ?5. Figure 2 ?5: Principle UV nanoimprint lithography process Ref: based on L Jay Guo, Recent progress in nanoimprint technology and its applications, J. Phys. D: Appl. Phys. 37 (2004) Master template importance could be mentioned and extended (1 page). This high resolution master template is used to imprint the arrays of FP-filter cavities for the fabrication of nanospectrometer. The principle operation of the fabricated nanospectrometer is illustrated in Figure 2 ?6. Figure 2 ?6: Principle of Nanospectrometer based on the FP-filter array fabricated by nanoimprint lithography 2.3 Technique of Master template fabrication In this section, various physical and chemical processes such as cleaning, spin coating, optical lithography, etching, lift-off, and optical characterization are implemented in the clean room to produce a master template. 2.3.1 Optical lithography One of the important processes in micro- and nano device fabrication is the optical lithography. In this process, the desire structures and patterns are transferred on to the substrate. The optical lithography includes spin coating, alignment and UV exposure in mask aligner and development in a developer solution [Ref: Principle of lithography by Harry J. Levinson]. Spin coating process involves dispensing few drops of a photo sensitive material called photoresist on top of the substrate and spinning it at a high speed to receive a thin film of the photoresist. The thickness and uniformity of the resulting film depends on the viscosity of the photoresist and the speed of the rotation [Ref: Fundamental principles of optical lithography: The science of microfabrication by Chris Mack]. The spin coating process is illustrated in Figure 2 ?7. Figure 2 ?7: Spin coating process Reference: (http://memscyclopedia.org/figure/3Spin-coating.svg) The obtained thin film of the photoresist after spin coating is exposed to UV radiation through a mask containing the desired structures in mask aligner (MA4). The exposure time plays an important role in the quality of the patterning process as explained in the next chapter. Based on type of the photoresist, exposure to UV radiation changes its chemical properties such as solubility in solutions [Ref: Fundamental principles of optical lithography: The science of microfabrication by Chris Mack]. After exposure to UV, the development process is carried out. In development process, the sample is washed in a developer so that the desired structures appear. If the exposed areas of photoresist are washed away during the development, the photoresist type is positive and if the exposed areas stay after the development process and the unexposed areas are washed away, the photoresist type is negative [Ref: The physics of micro/nano- fabrication by Ivor Brodie, Julius J. Muray]. This phenomenon is illustrated in Figure 2 ?8. Figure 2 ?8: Development process of photoresist. [Reference: http://www.enftech.com/eng/product/product01.aspx] 2.3.2 Reactive ion etching (RIE) Short theory of Reactive ion etching could be included (2 pages). Figure 2 ?9: Principle operation of RIE Reference: http://www.emeraldinsight.com/content_images/fig/0870220101015.png Parallel plate reactor 2.4 White light interferometer (WLI) Theory of WLI with figure could be given briefly (2 pages).