arizona state university bubble memory cmos charge pump copper ddr sdram delay line memory drum memory dynamic random access memory eeprom eprom ferroelectric ram flash memory infineon technologies integrated circuit layout ion magnetic core memory magnetoresistive random access memory memory cell micron technology nano-ram nanoionics nanowire non-volatile memory phase-change memory plated wire memory programmable read-only memory qimonda racetrack memory read-only memory resistive random-access memory sonos selectron tube semiconductor fabrication plant silver static random access memory thin film transistor tungsten twin transistor ram twistor memory volatile memory williams tube z-ram