The development of the microwave kinetic inductance detector (MKID) has renewed interest in bolometric infrared detectors based on thin films of YBa2Cu3O7-x (YBCO) high temperature superconductor (HTS). A compelling advantage of HTS bolometers is that they can be operated at temperatures of around 50 K, which significantly reduces the complexity of the cooling requirements. To be viable for large-scale production of HTS bolometer detector arrays, high-quality, thin YBCO films are required on large-area Si wafers for increased throughput and to fabricate the membrane structures that support the YBCO bolometers. YBCO deposition on Si requires optimized MgO buffer layers deposited using ion beam assisted deposition (IBAD). Currently there is no domestic commercial source for YBCO films. In Phase I, we propose to improve the uniformity of currently available YBCO films on Si, and to design an innovative reactive co-evaporation system for the deposition of high-quality films of YBCO on large-area substrates that will be built and commissioned in Phase II.