The Ga 2 O 3 solar-blind photodetectors (SBPDs) face the tradeoff between power consumption (<inline-formula> <tex-math notation="LaTeX">P_{\text {C}} </tex-math></inline-formula>) and photoresponse ...performance. Here, an ultrasensitive two-terminal photodetector based on <inline-formula> <tex-math notation="LaTeX">\boldsymbol {\beta } </tex-math></inline-formula>-Ga 2 O 3 microflake with extremely-low working voltage and <inline-formula> <tex-math notation="LaTeX">{P}_{\text {C}} </tex-math></inline-formula> was achieved. At a working voltage of 2 V and <inline-formula> <tex-math notation="LaTeX">{P}_{\text {C}} </tex-math></inline-formula> of 10 fW, the Ga 2 O 3 SBPD exhibits superexcellent photodetection performance, including a responsivity (<inline-formula> <tex-math notation="LaTeX">{R} </tex-math></inline-formula>) of <inline-formula> <tex-math notation="LaTeX">{2.3}\,\,\times \,\,{10}^{{5}}\text{A} </tex-math></inline-formula>/W, a detectivity (<inline-formula> <tex-math notation="LaTeX">{D}^{ \boldsymbol {\ast }} </tex-math></inline-formula>) of <inline-formula> <tex-math notation="LaTeX">{3.5}\,\,\times \,\,{10}^{{18}} </tex-math></inline-formula> Jones, a photo-to-dark-current ratio ( PDCR ) of <inline-formula> <tex-math notation="LaTeX">{3.2}\,\,\times \,\,{10}^{{8}} </tex-math></inline-formula>, and an ultra-low dark current (<inline-formula> <tex-math notation="LaTeX">{I}_{\text {dark}} </tex-math></inline-formula>) of 5 fA. Strikingly, the device keeps satisfactory performance at ultralow working voltage of 0.01 V, including a <inline-formula> <tex-math notation="LaTeX">{P}_{\text {C}} </tex-math></inline-formula> of 0.05 fW, a <inline-formula> <tex-math notation="LaTeX">{R} </tex-math></inline-formula> of <inline-formula> <tex-math notation="LaTeX">{2.4}\,\,\times \,\,{10}^{{3}} </tex-math></inline-formula> A/W, a <inline-formula> <tex-math notation="LaTeX">{D}^{ \boldsymbol {\ast }} </tex-math></inline-formula> of <inline-formula> <tex-math notation="LaTeX">{5.6}\,\,\times \,\,{10}^{{16}} </tex-math></inline-formula> Jones, and a PDCR of <inline-formula> <tex-math notation="LaTeX">{3.4}\,\,\times \,\,{10}^{{6}} </tex-math></inline-formula>. The superior solar-blind sensitivity makes it the most excellent Ga 2 O 3 detector towards high-performance and low-<inline-formula> <tex-math notation="LaTeX">P_{\text {C}} </tex-math></inline-formula> SBPD applications.
Mechanically exfoliated gallium oxide (Ga 2 O 3 ) nano sheets based filed-effect-transistors (FETs) with Al 2 O 3 /Ga 2 O 3 , indium gallium zinc oxide (IGZO)/Ga 2 O 3 n-n, and SnO/Ga 2 O 3 p-n ...heterojunctions in the back-channel were fabricated. In contrast to that Al 2 O 3 /Ga 2 O 3 heterojunction induces negative threshold voltage (<inline-formula> <tex-math notation="LaTeX">{V} _{\text {TH}} </tex-math></inline-formula>) shift, both IGZO/Ga 2 O 3 n-n and SnO/Ga 2 O 3 p-n heterojunctions shift <inline-formula> <tex-math notation="LaTeX">{V} _{\text {TH}} </tex-math></inline-formula> positively. The Ga 2 O 3 FET with 12 nm p-type SnO realizes enhanced-mode operation with <inline-formula> <tex-math notation="LaTeX">{V} _{\text {TH}} </tex-math></inline-formula> of 5.3 V by significantly shifting <inline-formula> <tex-math notation="LaTeX">{V} _{\text {TH}} </tex-math></inline-formula> of 40.3 V, high on current density of 14.1mA/mm, and high electron mobility of 191 cm 2 V −1 s −1 , which is, to the best of our knowledge, the highest among the reported Ga 2 O 3 FETs measured at room temperature.
Inorganic Bi‐based perovskites have shown great potential in X‐ray detection for their large absorption to X‐rays, diverse low‐dimensional structures, and eco‐friendliness without toxic metals. ...However, they suffer from poor carrier transport properties compared to Pb‐based perovskites. Here, we propose a mixed‐halogen strategy to tune the structural dimensions and optoelectronic properties of Cs3Bi2I9−nBrn (0≤n≤9). Ten centimeter‐sized single crystals are successfully grown by the Bridgman technique. Upon doping bromine to zero‐dimensional Cs3Bi2I9, the crystal transforms into a two‐dimensional structure as the bromine content reaches Cs3Bi2I8Br. Correspondingly, the optoelectronic properties are adjusted. Among these crystals, Cs3Bi2I8Br exhibits negligible ion migration, moderate resistivity, and the best carrier transport capability. The sensitivities in 100 keV hard X‐ray detection are 1.33×104 and 1.74×104 μC Gyair−1 cm−2 at room temperature and 75 °C, respectively, which are the highest among all reported bismuth perovskites. Moreover, the lowest detection limit of 28.6 nGyair s−1 and ultralow dark current drift of 9.12×10−9 nA cm−1 s−1 V−1 are obtained owing to the high ionic activation energy. Our work demonstrates that Br incorporation is an effective strategy to enhance the X‐ray detection performance by tuning the dimensional and optoelectronic properties.
Upon doping bromine into zero‐dimensional Cs3Bi2I9 (space group P63/mmc), the crystal structure transforms into a two‐dimensional layer structure as the bromine content reaches Cs3Bi2I8Br. At this optimized composition the Cs3Bi2I8Br single crystal has an outstanding detection performance in terms of record sensitivity for 100 keV hard X‐rays, ultralow detection limit, and excellent imaging capability at 75 °C.
A bulk-size single crystal of Y2Mo4O15 with 20 × 11 × 8 mm3 was successfully grown by the top-seed solution growth (TSSG) method. The full-width at half maximum of (100) and (010) crystal faces is 37 ...and 27 arcsec, respectively. The thermal conductivity coefficients κ11, κ22, κ33, and κ13 are determined to be 1.519, 2.097, 0.445, and 0.997 W m−1 K−1, respectively. It is worth noting that the Y2Mo4O15 crystal shows significant anisotropy thermal expansion properties, which exhibits a negative thermal expansion along the b-axis (α22 = −5.11 × 10−6 K−1). The crystal structure analysis shows that the shrinking of Mo–O bond lengths along the b-axis with the increasing temperature would be the main origin of the negative thermal expansion properties for Y2Mo4O15 crystal, which does not comply with the current mechanism.
An intriguing reversible band gap narrowing behavior of the lead‐free hybrid perovskite single crystal DMASnI3 (DMA=CH3NH2CH3+) from yellow to black is observed without phase transformation. We ...discuss the transformation mechanism in detail. More interestingly, the transformed samples in black can rapidly self‐heal into yellow ones when exposed to deionized water (DI water). Contrary to other hybrid perovskites, DMASnI3 crystals exhibit excellent water phase stability. For example, DMASnI3 was immersed in DI water for 16 h and no decomposition was observed. Inspired by its excellent water phase stability, we demonstrate a potential eco‐friendly application of DMASnI3 in photo‐catalysis for H2 evolution in DI water. We present the first H2 evolution rate of 0.64 μmol h−1 with good recycling properties for pure DMASnI3 crystals. After the narrowing process, the optical band gap of DMASnI3 can be lowered from 2.48 eV to 1.32 eV. Systematical characterizations are applied to investigate their structures and optoelectronic properties. The reversible band gap narrowing behavior and outstanding electrical properties, such as higher carrier mobility and long carrier lifetime show that DMASnI3 has a great potential for optoelectronic applications.
Reversible band gap narrowing behavior of Sn‐based hybrid perovskite single crystal was first revealed with excellent phase stability, narrow band gap, higher carrier mobility and longer carrier lifetime. This is encouraging for the optoelectronic application.
Metal halide perovskite single crystals are promising for hard X‐ray detection, but growth of large‐sized thin single crystals and inhibition of halide ion migration under high bias are challenging. ...Herein, the preparation of dense stacking of oriented millimeter‐sized perovskite single crystals with capability of large‐area fabrication, controlled thickness, and high ion migration activation energy (Ea)is reported. The oriented growth results in absence of grain boundaries parallel with the substrates, leading to large carrier mobility‐lifetime (µτ) product of 2.7 × 10−3 cm2 V−1, which is comparable to values of many perovskite bulk single crystals. Under low bias, hard X‐ray detectors exhibit high sensitivity of 1.2 × 104 µC Gy−1 cm−2 and low detection limit of 87.5 nGy s−1, which are comparable to those of many single‐crystal hard X‐ray detectors under high bias. Moreover, combination of low bias and high Ea results in weak halide ion migration and small dark current drift of 3.2 × 10−4 nA cm−1 s−1 v−1. Benefited from the superior detector performance, high‐contrast hard X‐ray imaging can be obtained at a low dose rate of 1.26 µGy s−1. The work may promote the application of perovskite hard X‐ray detectors in practical imaging area.
Dense stacking of oriented millimeter‐sized perovskite single crystals with the capability of large‐area fabrication, controlled thickness, high ion migration activation energy, and large carrier mobility products are in situ grown on ITO substrate. 120 kV hard X‐ray detectors working under low bias exhibit high sensitivity, low detection limit, and small dark current drift.
β-Ga
2
O
3
, a semiconductor material, has attracted considerable attention given its potential applications in high-power devices, such as high-performance field-effect transistors. For decades, ...β-Ga
2
O
3
has been processed through chemical mechanical polishing (CMP). Nevertheless, the understanding of the effect of OH
−
on β-Ga
2
O
3
processed through CMP with an alkaline slurry remains limited. In this study, β-Ga
2
O
3
substrates were successively subjected to mechanical polishing (MP), CMP and etching. Then, to investigate the changes that occurred on the surfaces of the samples, samples were characterised through atomic force microscopy (AFM), three-dimensional laser scanning confocal microscopy (LSCM), scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). LSCM and SEM results showed that β-Ga
2
O
3
is highly vulnerable to brittle fracture during MP. AFM revealed that an ultrasmooth and nondamaged surface with a low
R
a
of approximately 0.18 nm could be obtained through CMP. XPS results indicated that a metamorphic layer, which mainly contains soluble gallium salt (Ga(OH)
4
−
), formed on the β-Ga
2
O
3
surface through a chemical reaction. A dendritic pattern appeared on the surface of β-Ga
2
O
3
after chemical etching. This phenomenon indicated that the chemical reaction on the β-Ga
2
O
3
surface occurred in a nonuniform and selective manner. The results of this study will aid the optimization of slurry preparation and CMP.
β-Ga
2
O
3
, a semiconductor material, has attracted considerable attention given its potential applications in high-power devices, such as high-performance field-effect transistors.
This work reports a <inline-formula> <tex-math notation="LaTeX">\beta </tex-math></inline-formula>-Ga 2 O 3 double-barrier Schottky barrier diode (DBSBD) with both low turn-on voltage and low reverse ...leakage current by using Ni and PtO x as the anode electrode. The barrier height of PtO x -based diode can be effectively modulated from 1.26 to 1.62 eV by adjusting oxygen pressure during sputtering processes. Combining the maximum work function of PtO x electrode with the optimization of the electrode ratio of Ni and PtO x , the DBSBD with an electrode diameter ratio of <inline-formula> <tex-math notation="LaTeX">\text{D}_{\text {Ni}} /\text{D}_{\text {PtOx}}= {75}/{150} \mu \text{m} </tex-math></inline-formula> not only exhibits a high forward current of 470.9 A/cm 2 (at 3.5 V), a low on-resistance of 4.1 <inline-formula> <tex-math notation="LaTeX">\text{m}\Omega ~\cdot </tex-math></inline-formula>cm 2 and a low turn-on voltage of 1.13 V, but also possesses a relatively low reverse leakage current of <inline-formula> <tex-math notation="LaTeX">{1.2}\times {10}^{-{7}} </tex-math></inline-formula> A/cm 2 (at −100 V), which is more than one order of magnitude lower than that of the Ni-SBD. Silvaco TCAD simulation reveals that such optimization can be attributed to the suppression of edge leakage current due to the double-barrier contact. Therefore, the strategy of double-barrier design can balance the forward and reverse characteristics in SBD, providing a new device structure for advanced power electronics.
Perovskite single crystals and polycrystalline films have complementary merits and deficiencies in X‐ray detection and imaging. Herein, we report preparation of dense and smooth perovskite ...microcrystalline films with both merits of single crystals and polycrystalline films through polycrystal‐induced growth and hot‐pressing treatment (HPT). Utilizing polycrystalline films as seeds, multi‐inch‐sized microcrystalline films can be in situ grown on diverse substrates with maximum grain size reaching 100 μm, which endows the microcrystalline films with comparable carrier mobility‐lifetime (μτ) product as single crystals. As a result, self‐powered X‐ray detectors with impressive sensitivity of 6.1×104 μC Gyair−1 cm−2 and low detection limit of 1.5 nGyair s−1 are achieved, leading to high‐contrast X‐ray imaging at an ultra‐low dose rate of 67 nGyair s−1. Combining with the fast response speed (186 μs), this work may contribute to the development of perovskite‐based low‐dose X‐ray imaging.
Dense, smooth, substrate‐integrated, large‐area and thickness‐controlled perovskite microcrystalline films are prepared. They are used as self‐powered microcrystalline X‐ray detectors with an impressive sensitivity of 6.1×104 μC Gyair−1 cm−2 and a low detection limit of 1.5 nGyair s−1, leading to high‐contrast X‐ray imaging at an ultra‐low dose rate of 67 nGyair s−1, which may further reduce the X‐ray radiation risk to patients.
The in‐plane anisotropic feature of 2D layered materials has captured enormous research interest due to their application in polarization‐sensitive photodetection. Here, silicon phosphide (SiP), as a ...novel member of group IV–V 2D materials, is first introduced to the anisotropic 2D materials family with a high in‐plane anisotropy. The low‐symmetry structure, optical and optoelectronic properties are investigated systematically. Impressively, the photodetectors based on 2D SiP demonstrate high performance with low dark current, a fast response speed of 30 µs, and a strong anisotropic photoresponse with an anisotropic factor of 2.9. Furthermore, a strong polarization‐sensitive photodetector with a dichroic ratio up to 2.3 is realized based on the intrinsic linear dichroism of 2D SiP. This work not only provides an insight into the in‐plane anisotropic properties of 2D SiP, but also sheds light on its great potentials in anisotropic optoelectronic applications.
Strong in‐plane anisotropy in the new 2D material SiP is studied. For the first time, a high performance photodetector based on 2D SiP with fast response speed (30 µs), strong anisotropy photoresponse and sensitive polarization photoresponse is fabricated. This work provides a broad prospect for 2D SiP in anisotropic optoelectronic applications.
PDF
