Type II Superlattice Avalanche Photodiodes

Type-II superlattice avalanche photodiodes have shown advantages compared to conventional mercury cadmium telluride photodiodes for infrared wavelength detection. However, surface or interface leakage current has been a major issue for superlattice avalanche photodiodes, especially in infrared wavelength region. First, passivation of the superlattice device with ammonium sulfide and thioacetamide was carried out, and its surface quality was studied by X-ray Photoelectron Spectroscopy. The study showed that both ammonium sulfide and thiacetamide passivation can actively remove the native oxide at the surface. Thiacetamide passivation combine more sulfur bonds with III-V elements than that of ammonium sulfide. Another X-ray photoelectron spectra of thiacetamide-treated atomic layer deposited zinc sulfide capped InAs/GaSb superlattice was performed to investigate the interface sulfur bond conditions. Sb–S and As–S bonds disappear while In-S bond gets enhanced, indicating that Indium Sulfide should be the major components at the interface after ZnS deposition. Second, the simulation of electrical characteristics for zinc sulfide, silicon nitride and silicon dioxide passivated superlattice devices was performed by SILVACO software to fit the experimental results and to discover the surface current mechanism. Different surface current mechanism strengths were found. Third, several novel dual-carrier avalanche photodiode structures were designed and simulated. The structures had alternate carrier multiplication regions, placed next to a wider electron multiplication region, creating dual-carrier multiplication feedback systems. Gain and excess noise factor of these structures were simulated and compared based on the dead space multiplication theory under uniform electric field. From the simulation, the applied bias can be greatly lowered or the thickness can be shrunk to achieve the same gain from the conventional device. The width of the thin region was the most critical parameter determining the device performance

Total Syntheses of Nannocystins A and A0, Two Elongation Factor 1 Inhibitors

Asymmetric total syntheses of nannocystins A and A0 were achieved in a convergent route starting from simple materials. Nannocystin family natural products bear potent anticancer activity as elongation factor 1 inhibitors. In this synthesis, the challenging tertiary amide bond was constructed by peptide coupling between an acyl chloride and a secondary amine. A late-stage ring-closing metathesis reaction successfully rendered the macrocycle. This efficient synthetic strategy should be applicable to other nannocystins and analogues and therefore should benefit future structure–activity relationship studies

Total Syntheses of Nannocystins A and A0, Two Elongation Factor 1 Inhibitors

Asymmetric total syntheses of nannocystins A and A0 were achieved in a convergent route starting from simple materials. Nannocystin family natural products bear potent anticancer activity as elongation factor 1 inhibitors. In this synthesis, the challenging tertiary amide bond was constructed by peptide coupling between an acyl chloride and a secondary amine. A late-stage ring-closing metathesis reaction successfully rendered the macrocycle. This efficient synthetic strategy should be applicable to other nannocystins and analogues and therefore should benefit future structure–activity relationship studies

Modeling and Simulation of Long‐Wave Infrared InAs/GaSb Strained Layer Superlattice Photodiodes with Different Passivants

Current-voltage characteristics of long-wave infrared (LWIR) InAs/GaSb strained layer superlattice photodiodes (cut-off wavelength ~10 μm), passivated with different surface passivants, have been modeled and simulated using ATLAS software from SILVACO. The simulated results are fitted to previous experimental results obtained on unpassivated devices and those passivated by silicon-dioxide (SiO2), silicon nitride (SixNy) and zinc sulfide (ZnS). Surface parameters in terms of surface recombination velocity, shunt resistance and interface trap density are extracted for different passivants. The performance of silicon-dioxide passivated diode is solely dominated by a shunt leakage path with a shunt resistance value of 0.56 Ω-cm2. Extracted electron and hole surface recombination velocities have values of 105 cm/s and 107 cm/s for unpassivated, 103 cm/s and 105 cm/s for SixNy passivated and 102 cm/s and 103 cm/s for ZnS passivated devices. Interface trap density follows a similar trend with values of 1015 cm-2, 8.5×1014 cm-2 and 1010 cm-2 for unpassivated, SixNy passivated and ZnS passivated devices respectively. The suitability and limitations of the simulation tool are discussed

Teosinte unigenes' sequences

Due to the lack of available reference genome, clean reads from Zea may ssp. parviglumis and Zea mays ssp. mexicana were first de novo assembled into contigs using Trans-ABySS, which can use a multiple K-mer strategy to assemble the transcriptome. After that, transcriptome from different samples were pooled to reconstruct the transcriptome using CD-HIT-EST with a word length of 8 and an identity threshold ≥ 0.98.Sequentially, CAP3 was used to discard the redundancy transcripts, and the resulting contigs and singlets were combined to represent transcriptome of teosinte

Deeper Defluorination and Mineralization of a Novel PFECA (C7 HFPO-TA) in Vacuum UV/Sulfite: Unique Mechanism of H/OCF₃ Exchange

C7 HFPO-TA is a newly identified alternative to PFOA, which possesses a unique structure fragment (CF3O–CF(CF3)−). In this study, we evaluated the chemical reactivity of C7 HFPO-TA in advanced oxidation and reduction processes for the first time, which revealed a series of unexpected transformation mechanisms. The results showed that reductive degradation based on hydrated electrons (eaq–) was more feasible for the degradation of C7 HFPO-TA. For oxidative degradation, the branched −CF3 at the α-position carbon posed as the spatial hindrance, shielding the attack of SO4•– to −COO–. The synergistic effects of HO•/eaq– and direct photolysis led to deeper defluorination and mineralization of C7 HFPO-TA in the vacuum UV/sulfite (VUV/SF) process. We identified a unique H/OCF3 exchange that converted the CF3O–CF(CF3)- into H–CF(CF3)- directly, and the SO3•– involved mechanism of C7 HFPO-TA for the first time. We revealed the branched −CF3 connected to the same carbon next to the CF3O- group affected the C–O bond cleavage site, preferring the H/OCF3 exchange pathway. The defluorination of C7 HFPO-TA was compared with PFOA and three PFECAs in the VUV/SF process, which was highly dependent on structures. Degradation kinetics, theoretical calculations, and products’ analysis provided an in-depth perspective on the degradation mechanisms and pathways of C7 HFPO-TA

Total Synthesis of Penicibilaenes Enabled by a Tandem Double Conia-ene Type Reaction

The total syntheses of penicibilaenes A and B are described. The key step is the tBuOK/DMSO-mediated tandem 5-exo-dig Conia-ene type reaction and 6-exo-dig Conia-ene type reaction to install the tricyclic [6.3.1.01,5] dodecane core of penicibilaenes from dibutynyl cyclohexanone in a single step, together with a sequence of copper-mediated conjugate addition and Crabtree’s hydrogenation to forge the stereogenic centers at C5 and C2, respectively

Zea mays ssp. parviglumis unigenes' sequences

Due to lack of available reference genome, clean reads from 3 Zea mays ssp. parviglumis were first de novo assembled into contigs using Trans-ABySS. After discarding the contigs <200 bp, the remaing contigs were then assembled into unigenes, whcih represented the individual transcriptome at the seedling stage. To obtain the transcriptomes from Zea mays ssp. parviglumis, individual transcriptomes were pooled to reconstruct the transcriptome using CD-HIT-EST with a word length of 8 and an identity threshold ≥ 0.98. Sequentially, CAP3 was used to discard the redundancy transcripts, and the resulting contigs and singlets were combined to represent Zea mays ssp. parviglumis transcriptome