Glancing Angle Deposition (GLAD) with a Variable Angle Stage | Dr. Steven Jim
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3 (of 6) Scanning Electron Microscope Images of GLAD nanostructures (vertical 'blade’, vertical post, and chevron) reprinted with permission from S.R. Jim, M.T. Tashchuk, G.E. Morlock, Louis W. Bezuidenhout, Wolfgang Schwack, and Michael J. Brett, “Engineered Anisotropic Microstructures for Ultrathin-Layer Chromatography,” Analytical Chemistry. 82(12), pp 5349-5356 (June 1, 2010). DOI: https://doi.org/10.1021/ac101004b
3 (of 6) Scanning Electron Microscope Images of GLAD nanostructures (Slanted posts, Bragg stacks, and helices) reprinted with permission from Peter C.P. Hrudey, Andy C. van Popta, Jeremy C. Sit, Michael J Brett, “Photonic device applications of nano-engineered thin film materials,” Proceedings. 5931, Nanoengineering: Fabrication, Properties, Optics, and Devices II; 593113. Optics and Photonics, San Diego (2005). DOI: https://doi.org/10.1117/12.622281
"GLAD"
"Glancing Angle Deposition"
"Thin Film Evaporation"
"Nanofabrication"
"Steven Jim"
"Physical Vapor Deposition"
"UCI"
"Unversity California Irvine"
Transcript:
Hello, welcome to the University of California Irvine, in beautiful wonderful sunny Irvine California. My name is Steven Jim and I’m a postdoctoral researcher in professor Alon Gorodetsky’s group. It’s my pleasure to tell you about our amazing Angstrom Engineering vacuum deposition tool. The tool itself is optimized for a very powerful technique for making nanostructure thin films called glancing angle deposition. This technique is performed inside of a vacuum chamber that was precision-designed by the Angstrom Engineering team. It allows us to fabricate complicated microstructures across relatively large areas such as four or six-inch silicon wafer. When you look at these structures under an electron microscope, they tend to look a lot like shag carpets, with very carefully sculpted yarns. These microstructures can be sculpted into a variety of complex shapes, such as vertical posts, zigzags, or even helices. What makes this technique so powerful is that those types of microstructures can be made from a variety of different materials. These include silicon dioxide, titanium dioxide, different metals, there’s a whole host of different materials that have been used in this process. Some of these structures are very hard or in fact impossible to make using different techniques other than glancing angle deposition. But in all of these cases, these nano-structured thin films are deposited in a vacuum chamber like this, onto a flat substrate such as a silicon wafer, or a glass microscope slide. But what makes glancing angle deposition special, is that we would have that vapor flux arrive at a highly oblique angle so that those new nuclei will grow and cast little shadows into which further material cannot be deposited, and as a result these little nuclei will grow into angled columnar structures that are pointing towards the apparent source of that vapor. That phenomenon has been known for many decades now, but where GLAD really takes that phenomenon and turns it into a powerful technique is by introducing a precisely designed rotation algorithm on top of that tilting algorithm.
As a result, we can take those angular structures, and sculpt them into those more exotic structures like those zigzags and helices that make GLAD so special. Glancing angle deposition is a technique that has been around for almost two decades. It’s a well-established technique studied by dozens of research groups around the world and what all of these groups have in common is their use of a variable angle stage such as the one found on an evaporator like ours, provided by Angstrom Engineering.
So now that I’ve told you a little about GLAD, why don’t I take you around to the back of our system so we can take a peek inside. OK, so let’s take a look inside of the position chambers. We’ll just pop the latches. Here it is.
In order to arrive at this layout, we worked with the Angstrom Engineering team to convey the important design considerations when it came to optimizing our system for glancing angle deposition. So at the very bottom here we can see our electron beam evaporation source, the main workhorse of the system. Off to the sides, we have three thermal evaporation sources and together all of those sources give us the ability to deposit a variety of different materials; metals, non-metals, organics, and all of these sources direct their evaporation flux towards the substrate holder attached to our variable angle stage. The variable angle stage allows for coating over non-uniform topologies but it was optimized in our case to not only cover edged features and silicon wafers or MEMs devices, but it was optimized to fabricate a glancing angle deposition thin films.
In glancing angle deposition, precision is paramount. When we’re depositing materials at a highly oblique tilt angle; angles in excess of 80°.