Flexible ultraviolet (UV) photodetectors (PDs) have gained increasing demand because of their widespread applications in wearable devices. However, difficulties associated with complicated fabrication technologies significantly limit their scope of application. Herein, via the development of a femtosecond laser direct writing (FsLDW) strategy, silicon carbide (SiC) nanoparticles are found to be assembled in a single microwire within 30 s. The surface of the deposited SiC microwire presents a three-dimensional porous structure, which is conducive to improving the responsivity of the device. The responsivity of a SiC-based microwire PD to UV light at 365 nm is found to be 55.89 A W−1 at a 1 V bias. The as-fabricated SiC microwire PDs on a glass substrate exhibit thermal stability at 350 °C, and the response speed of the PDs becomes notably faster at high temperatures, suggesting their promising applications in harsh conditions. Due to the low-temperature processing characteristics of this process, they can be prepared not only on glass substrates, but also on thermosensitive polymer substrates without an extra transfer process. Moreover, the SiC microwires prepared via FsLDW are directly deposited on the flexible substrate, and the prepared flexible SiC-based PDs can still work stably after being bent 2000 times. This research unveils a feasible way to fabricate a PD with excellent thermal stability and mechanical flexibility.

Room-temperature fabrication of SiC microwire photodetectors on rigid and flexible substrates via femtosecond laser direct writing

Current electronic technology based on silicon is approaching its physical and scientific limits. Carbon-based devices have numerous advantages for next generation electronics (e.g., fast speed, low power consumption and simple process), that when combined with the unique nature of the versatile allotropes of carbon elements, are creating an electronics revolution. Carbon electronics are greatly advancing with new preparations and sophisticated designs. In this perspective, representatives with various dimensions, e.g., carbon nanotubes, graphene, bulk diamond, and their extraordinary performance, are reviewed. The associated state-of-the-art devices and composite hybrid all-carbon structures are also emphasized to reveal their potential in the electronics field. Advances in commercial production have improved the cost efficiency, material quality, and device design, accelerating the promise of carbon materials.

Carbon materials: The burgeoning promise in electronics

In this letter we investigate for the first time the behavioral differences of transport properties of electrons and holes observed in high-resolution radiation detectors fabricated on high-purity single crystalline diamond using biparametric (BP) correlation studies. The chemical vapor deposition (CVD) grown $500~\mu \text{m}$ thick diamonds exhibited an excellent energy resolution of 0.5% for 5486 keV alpha particles for both electron and hole transport in a vertical electrode geometry. Interestingly, the behavior of the electron and hole transport were found to be vastly different at bias voltages less than 100 V. No discernable detector signal was observed due to electron transit below an applied bias of −100 V. The hole transit on the other hand, resulted in resolvable pulse height spectrum (PHS) from bias voltages as low as +10 V. Digital biparametric correlation studies of the rise-times and induced charge from each interaction of the incident alpha particles, revealed that the observed difference is due to the excessive electron trapping below bias voltages of −100 V. At lower biases, the width of the alpha peak in the PHS due to hole movement, was hardly affected by trapping and was observed to be limited due to lower hole drift velocities. The developed method with new insights of correlating the biparametric plots and the detector performance can be extended to vast range of semiconductor detectors.

Behavioral Contrast of Electron and Hole Transport in High-Resolution Diamond Detectors: A Biparametric Correlation Study

Diamond radiation detectors (DRDs) based on type-IIa chemical vapor deposition (CVD) monocrystal diamond are more suitable for engineering applications with high consistency requirements due to the lower cost and property controllability. However, their saturated charge collection efficiencies (CCEs) have huge differences. Six type-IIa CVD monocrystal diamond plates were analyzed by the Fourier transform infrared spectrometer, high resolution x-ray diffraction, Raman spectroscopy, photoluminescence and secondary ion mass spectroscopy. Then DRDs were fabricated by them and the CCEs were measured under the irradiation of 241Am source. The results show that the most important factor restricting CCEs are the impurities in the diamond plates, while dislocations with a density <1 × 107 cm−2 for all samples have weaker impact in our case. The reason is that the carrier mobility-lifetime (μτ) product of diamond is more strongly influenced by impurities in this dislocation density range. Thinning diamond plate, if the thickness is kept above 100 μm, is not a good means to obtain high performance DRDs. Therefore, to further improve the detector performance, ultra-high purity diamond growth is most important. Moreover, a diamond test and selection scheme for high performance DRDs is also demonstrated.

https://iopscience.iop.org/article/10.1088/1361-6463/abd5e2/pdf

Device performance of chemical vapor deposition monocrystal diamond radiation detectors correlated with the bulk diamond properties

We report the performance of a single crystal diamond radiation detector with gold films on hydrogen-terminated diamond as electrical contacts and oxygen-terminated diamond as surface isolation between electrodes. The origin-symmetric current-voltage characteristics showed excellent Ohmic contact behavior. An extremely low dark current value of 7.46 × 10−13 A/mm2 was measured at an electric field of 1 V/μm. The charge collection efficiency and energy resolution of this detector were 99.01% and 1.5% for holes, and 98.6% and 1.7% for electrons under irradiation with 241Am α-particles. Under 60Co γ-ray irradiation with a dose rate of 1.271 Gy/s, the gain factor, specific sensitivities, and signal-to-noise ratio were 49.46, 12.43 μC/Gy·mm3, and 1 × 106 at 200 V bias voltage (0.66 V/μm), respectively. A rise time of 347.4 ps of the response to a pico-second pulsed electron source was also measured. This research provides a possibility to improve the performance of the diamond radiation detector through diamond surface modification.

Xiaoping Ouyang

Papers

High performance hydrogen/oxygen terminated CVD single crystal diamond radiation detector

Device performance of chemical vapor deposition monocrystal diamond radiation detectors correlated with the bulk diamond properties