Metal Dielectric Photonic Bandgap (MDPBG) Structures
Novel photonic structures with alternating thin film layers of metal and dielectric with precise thicknesses, termed Metal-Dielectric Photonic Bandgap (MDPBG) structures, have the potential to revolutionize the field of optical windows for civilian and military applications. MDPBG structures are very attractive for a wide variety of applications such as X-ray, microwave, infrared or other electromagnetic shielding, for sensor and eye protection, as transparent electrodes, and as super-lens that permit optical imaging at length scales well below the diffraction limit, or as highly-nonlinear and linear optical filters.
It is a daunting challenge to manufacture these structures because they need highly conducting metal thin films with a thickness below 10 nm, grown with good coverage, high conductivity and precise thickness control on insulator surfaces. Traditional physical vapor deposition (PVD) techniques have failed to meet the desired specs on metal films since their percolation limit is greater than 10 nm for a conducting film, especially on insulating surfaces.
RMD has developed novel atomic layer deposition (ALD) techniques for growing ultrathin metal films below the 10 nm thickness threshold. Some of the metals that RMD is currently working on are copper, silver and gold, which can be applied to MDPBG structures active in infrared and visible ranges. RMD is also developing ALD of insulator layers such that the metal-dielectric stack can be repeat-deposited in a single ALD system process without exposure to the ambient conditions, thereby boosting the performance.
Schematic of Metal-Dielectric Photonic Bandgap Structures, where the metals candidates are Cu, Ag, Au or Al with a single layer thickness < 10 nm. The dielectric candidates are SiO2, Al2O3 or HfO2. These layers are deposited using Atomic Layer Deposition (ALD) at RMD, for precise control on their thickness and contiguous films.