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A 512 512 CMOS active pixel sensor (APS) was designed and fabricated in a standard 0.5-m technology. The radiation tolerance of the sensor has been evaluated with Co-60 and proton irradiation with proton energies ranging from 11.7 to 59 MeV. The most pronounced radiation effect is the increase of the dark current. However, the total ionizing dose-induced dark current increase is orders of magnitude smaller than in standard devices. It behaves logarithmically with dose and anneals at room temperature. The dark current increase due to proton displacement damage is explained in terms of the nonionizing energy loss of the protons. The fixed pattern noise does not increase with total ionizing dose. Responsivity changes are observed after Co-60 and proton irradiation, but a definitive cause has not yet been established.

The low-frequency (LF) noise behavior of metal-oxide-semiconductor field-effect transistors (MOSFETs) is studied when cycled between inversion and accumulation. On large-area devices the decrease of the LF noise is systematically found, and supports the observations by Bloom and Nemirovsky [Appl. Phys. Lett. 58, 1664 (1991)]. The random telegraph signal (RTS) noise observed in small (submicrometer) devices disappears when the transistor is cycled into accumulation. The drop in LF noise observed may thus be explained by the fact that most or all of the RTSs, which are caused by carrier trapping into slow oxide states, no longer contribute to the noise of the system. The method indicates a possibility to separate the contributions of different sources of 1/f noise in MOSFETs.

Objective. Decoding neural activity has been limited by the lack of tools available to record from large numbers of neurons across multiple cortical regions simultaneously with high temporal fidelity. To this end, we developed the Argo system to record cortical neural activity at high data rates. Approach. Here we demonstrate a massively parallel neural recording system based on platinum-iridium microwire electrode arrays bonded to a CMOS voltage amplifier array. The Argo system is the highest channel count in vivo neural recording system, supporting simultaneous recording from 65 536 channels, sampled at 32 kHz and 12-bit resolution. This system was designed for cortical recordings, compatible with both penetrating and surface microelectrodes. Main results. We validated this system through initial bench testing to determine specific gain and noise characteristics of bonded microwires, followed by in-vivo experiments in both rat and sheep cortex. We recorded spiking activity from 791 neurons in rats and surface local field potential activity from over 30 000 channels in sheep. Significance. These are the largest channel count microwire-based recordings in both rat and sheep. While currently adapted for head-fixed recording, the microwire-CMOS architecture is well suited for clinical translation. Thus, this demonstration helps pave the way for a future high data rate intracortical implant.