A Maskless Photolithography Apparatus for the Microfabrication of Electrical Leads

Graphene is a new and exciting, two-dimensional material. Particularly interesting are the electrical features of graphene. The small size of graphene used in this experiment (on the scale of microns) presents the need for small electrical leads. Photolithography can be used to make appropriately sized leads by depositing metal onto substrates in specific patterns. The technique uses light to transfer geometric patterns onto a light sensitive photoresist on the surface of a substrate. We have built a low cost, maskless photolithography apparatus assembled from a computer, a consumer grade projector, and a microscope. With multiple exposures, we can make features ranging from approximately 1 μm to 785 μm. The 1 μm feature size is near the theoretical minimum for the wavelength of blue light used, and will be more than sufficient for contacting the flakes of graphene, which average 50 μm in size

Graphene: Gas Detector

The resistivity of graphene is sensitive to the presence of gas molecules adsorbed on it. Since graphene is one atom thick, a gas detector made from it might be sensitive to the presence of even single molecules of gas. We developed early stage devices for this purpose. This led us to future directions for research

Building and Testing a Photolithography System

Photolithography is a technique used to deposit metals onto substrates in specific patterns. The process uses light to transfer geometric patterns onto a light sensitive photoresist on the surface of a substrate. We have built a low-cost, maskless photolithography system assembled from a computer, a consumer projector, and a microscope. The photoresist is spun in a modified food processor and baked on a standard hot plate. Exposing the photoresist only takes a few minutes and allows for multiple runs on the same substrate in a short amount of time. Through multiple exposures, we can make features ranging from approximately 1 μm to 785 μm, which is especially useful when making contacts using the large features. The goal for this photolithography system is to make small electrical leads to study graphene, a two-dimensional material