The electronic conduction through a ${\mathrm{Pr}}_{0.7}{\mathrm{Ca}}_{0.3}\mathrm{Mn}{\mathrm{O}}_3$ thin film is investigated by measurements using dc and pulsed biases. Semiconducting ${\mathrm{Pr}}_{0.7}{\mathrm{Ca}}_{0.3}\mathrm{Mn}{\mathrm{O}}_3$ films sandwiched by electrodes show both hysteretic and asymmetric behaviors in current-voltage characteristics. The observed conduction characteristics exhibit the space-charge-limited-current effect, and the hysteretic behavior can be ascribed to a carrier trapping and detrapping of the trap sites in the manganite. The hysteresis induces a colossal electroresistance (CER) of more than 5000% at room temperature. The CER ratio is independent of the duration time of pulses from an infinite (dc) down to $150\mathrm{ns}$, indicating that the carrier filling of all the traps can be completed within a short time.

The electroforming and the resistance-switching behaviors in magnetite, ${\mathrm{Fe}}_3{\mathrm{O}}_4$ , by the application of an appropriate electric field are demonstrated on a lateral device with multiple electrodes. By means of this device, both the location and the nature of the change in ${\mathrm{Fe}}_3{\mathrm{O}}_4$ are specified from the electrical measurements and Raman spectroscopy. The switching phenomenon is caused in maghemite, $\gamma \text{-}{\mathrm{Fe}}_2{\mathrm{O}}_3$ , which is formed by oxidation of ${\mathrm{Fe}}_3{\mathrm{O}}_4$ , near an interface of an anode. The authors argue that the switching motion is originated in a redox reaction between the ${\mathrm{Fe}}_3{\mathrm{O}}_4$ and $\gamma \text{-}{\mathrm{Fe}}_2{\mathrm{O}}_3$ .

The transient response during resistance switching in Ag∕Pr0.7Ca0.3MnO3∕Pt thin films is investigated by measurements using pulsed voltage biases. Semiconducting Pr0.7Ca0.3MnO3 (PCMO) films sandwiched by Ag and Pt electrodes show nonvolatile resistance switching (two orders of magnitude) as a result of applying pulsed voltage biases, even at room temperature. The transient responses of the voltage across the PCMO for a set (positive) and a reset (negative) pulse application are consistent with the resistance-switching behavior and show quite fast switching (3–100 ns) for the set pulse application, compared with 60–135 ns for the reset pulse application. The large resistance-switching ratio is saturated after a finite transient time, indicating that the carrier filling of the trap sites into PCMO is completed within quite a short time.

We have developed a real time ultraviolet (UV) imaging system that can visualize both invisible UV light and a visible (VIS) background scene in an outdoor environment. As a UV/VIS image sensor, an organic photoconductive film (OPF) imager is employed. The OPF has an intrinsically higher sensitivity in the UV wavelength region than those of conventional consumer Complementary Metal Oxide Semiconductor (CMOS) image sensors (CIS) or Charge Coupled Devices (CCD). As particular examples, imaging of hydrogen flame and of corona discharge is demonstrated. UV images overlapped on background scenes are simply made by on-board background subtraction. The system is capable of imaging weaker UV signals by four orders of magnitude than that of VIS background. It is applicable not only to future hydrogen supply stations but also to other UV/VIS monitor systems requiring UV sensitivity under strong visible radiation environment such as power supply substations.

We have developed a direct time-of-flight (TOF) 250 m ranging Complementary Metal Oxide Semiconductor (CMOS) image sensor (CIS) based on a 688 × 384 pixels array of vertical avalanche photodiodes (VAPD). Each pixel of the CIS comprises VAPD with a standard four transistor pixel circuit equipped with an analogue capacitor to accumulate or count avalanche pulses. High power near infrared (NIR) short (<50 ns) and repetitive (6 kHz) laser pulses are illuminated through a diffusing optics. By globally gating the VAPD, each pulse is counted in the in-pixel counter enabling extraction of sub-photon level signal. Depth map imaging with a 10 cm lateral resolution is realized from 1 m to 250 m range by synthesizing subranges images of photon counts. Advantages and limitation of an in-pixel circuit are described. The developed CIS is expected to supersede insufficient resolution of the conventional light detection and ranging (LiDAR) systems and the short range of indirect CIS TOF.

We present robust pixel design methodologies for a vertical avalanche photodiode-based CMOS image sensor, taking account of three critical practical factors: (i) “guard-ring-free” pixel isolation layout, (ii) device characteristics “insensitive” to applied voltage and temperature, and (iii) stable operation subject to intense light exposure. The “guard-ring-free” pixel design is established by resolving the tradeoff relationship between electric field concentration and pixel isolation. The effectiveness of the optimization strategy is validated both by simulation and experiment. To realize insensitivity to voltage and temperature variations, a global feedback resistor is shown to effectively suppress variations in device characteristics such as photon detection efficiency and dark count rate. An in-pixel overflow transistor is also introduced to enhance the resistance to strong illumination. The robustness of the fabricated VAPD-CIS is verified by characterization of 122 different chips and through a high-temperature and intense-light-illumination operation test with 5 chips, conducted at 125 °C for 1000 h subject to 940 nm light exposure equivalent to 10 kLux.