Adaptive GHz Devices
Abstract
a. Technical: This research project is to fabricate reconfigurable switches based on strain-engineered interfacial phase-change materials operating in GHz regime. Reconfigurable GHz component is one the critical features in electromagnetic maneuverability. The current technical challenges include switching energy, speed, dynamical range, size, and weight. The proposed component will be small size and light weight due to the nature of fabrication process. The objective of this research is to reduce the switching energy of phase change materials in reconfigurable RF switches by an order of magnitude and increase the number of switch cycles, whilst maintaining a 30 dB modulation depth at 10 GHz. The key problem with the current GeTe-based phase change material is the high energy required to melt the GeTe crystal, because the energy is wasted by fully melting the GeTe crystal in 3D, when in fact the electrical permittivity switching can be achieved by simply disrupting the weaker Ge-Te resonant bonds. The uniqueness of this proposal is to replace the GeTe layer in the RF-switches with a strain-engineered interfacial phase change material (iPCM) in the Sb2Te3-GeTe superlattice. The iPCMs confine the phase transition to 0.5 nm thick layers of GeTe within a Sb2Te3-GeTe superlattice structure. Confining phase transitions to the interface between two different materials limits the number of transitional microstates, and thus reduces the entropy change between the states. These 2D phase transitions waste less energy than their 3D counterparts because the whole superlattice structure does not melt, and the disorder occurs only at the GeTe interface layers. In addition, the switching energy for the interfacial phase change material can be further reduced by strain engineering. The strain-engineered Sb2Te3-GeTe switching time can be reduced to 5 ns, i.e. much shorter pulse. Further, lower energy switching pulses tend to increase the switching cycle endurance, thus these interfacial phase change RF-switches are expected to exhibit a higher cycleability than the current GeTe-based RF switches. In fabrication, the PI proposed to use Pulsed Laser Epitaxy (PLE) to grow the chalcogenide monolayer crystals and heterostructure superlattices over a wide range of growth conditions. PLE has the advantage that films with complex composition can be grown stoichiometrically over a huge pressure range, and the PLE deposition rate is easily control. A fractional factorial technique will be used to optimize the chalcogenide crystal quality. The fractional factorial design methods are very useful for quickly exploring the process optimization conditions for growing a new crystal material. Reconfigurable GHz components have many potential applications including communications, sensing, EM countermeasures, and IoT. The PI will work closely with Dr. James Champlain at NRL. The RF switches will be characterized at both SUTD and NRL. A potential transition path is Robert Young~s group at Northrop Grumman in Baltimore, to replace the GeTe in RF switch with the strain-engineered interfacial phase-change superlattices (Sb2Te3-GeTe). I strongly recommend funding this project. b. Relevance: This is one of the critical RF components relevant to EM situational awareness and EM spectrum management. c. Coordination: ONR Code 31 and 30. d. Desired Outcome: Journal publication. Delivery of sample to NRL and test at NRL.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Dec 17, 2018
- Source ID
- N629091912005
Entities
People
- Robert Simpson
Organizations
- Office of Naval Research
- Singapore University of Technology and Design
- United States Navy