First-principles study of oxygen vacancy defects in orthorhombic Hf0.5_{0.5}Zr0.5_{0.5}O2_2/SiO2_2/Si gate stack

The gate defect of the ferroelectric HfO$_2$-based Si field-effect transistor (Si FeFET) plays a dominant role in its reliability issue. The first-principles calculations are an effective method for the atomic-scale understanding of gate defects. However, the first-principles study on the defects of FeFET gate stacks, i.e., metal/orthorhombic-Hf$_{0.5}$Zr$_{0.5}$O$_2$/SiO$_2$/Si structure, has not been reported so far. The key challenge is the construction of metal/orthorhombic-Hf$_{0.5}$Zr$_{0.5}$O$_2$/SiO$_2$/Si gate stack models. Here, we use the Hf$_{0.5}$Zr$_{0.5}$O$_2$(130) high-index crystal face as the orthorhombic ferroelectric layer and construct a robust atomic structure of the orthorhombic-Hf$_{0.5}$Zr$_{0.5}$O$_2$/SiO$_2$/Si gate stack without any gap states. Its high structural stability is ascribed to the insulated interface. The calculated band offsets show that this gate structure is of the type-I band alignment. Furthermore, the formation energies and charge transition levels (CTLs) of defects reveal that the oxygen vacancy defects are more favorable to form compared with other defects such as oxygen interstitial and Hf/Zr vacancy, and their CTLs are mainly localized near the Si conduction band minimum and valence band maximum, in agreement with the reported experimental results. The oxygen vacancy defects are responsible for charge trapping/de-trapping behavior in Si FeFET. This work provides an insight into gate defects and paves the way to carry out the first-principles study of ferroelectric HfO$_2$-based Si FeFET.Comment: 18 pages, 5 figure

Transcriptome analysis of stem development in the tumourous stem mustard Brassica juncea var. tumida Tsen et Lee by RNA sequencing

<p>Abstract</p> <p>Background</p> <p>Tumourous stem mustard (<it>Brassica juncea </it>var. <it>tumida </it>Tsen et Lee) is an economically and nutritionally important vegetable crop of the <it>Cruciferae </it>family that also provides the raw material for <it>Fuling </it>mustard. The genetics breeding, physiology, biochemistry and classification of mustards have been extensively studied, but little information is available on tumourous stem mustard at the molecular level. To gain greater insight into the molecular mechanisms underlying stem swelling in this vegetable and to provide additional information for molecular research and breeding, we sequenced the transcriptome of tumourous stem mustard at various stem developmental stages and compared it with that of a mutant variety lacking swollen stems.</p> <p>Results</p> <p>Using Illumina short-read technology with a tag-based digital gene expression (DGE) system, we performed <it>de novo </it>transcriptome assembly and gene expression analysis. In our analysis, we assembled genetic information for tumourous stem mustard at various stem developmental stages. In addition, we constructed five DGE libraries, which covered the strains <it>Yong'an </it>and <it>Dayejie </it>at various development stages. Illumina sequencing identified 146,265 unigenes, including 11,245 clusters and 135,020 singletons. The unigenes were subjected to a BLAST search and annotated using the GO and KO databases. We also compared the gene expression profiles of three swollen stem samples with those of two non-swollen stem samples. A total of 1,042 genes with significantly different expression levels occurring simultaneously in the six comparison groups were screened out. Finally, the altered expression levels of a number of randomly selected genes were confirmed by quantitative real-time PCR.</p> <p>Conclusions</p> <p>Our data provide comprehensive gene expression information at the transcriptional level and the first insight into the understanding of the molecular mechanisms and regulatory pathways of stem swelling and development in this plant, and will help define new mechanisms of stem development in non-model plant organisms.</p

Atomic Layer Deposition (ALD) of Metal Gates for CMOS

The continuous down-scaling of complementary metal oxide semiconductor (CMOS) field effect transistors (FETs) had been suffering two fateful technical issues, one relative to the thinning of gate dielectric and the other to the aggressive shortening of channel in last 20 years. To solve the first issue, the high-&kappa; dielectric and metal gate technology had been induced to replace the conventional gate stack of silicon dioxide layer and poly-silicon. To suppress the short channel effects, device architecture had changed from planar bulk Si device to fully depleted silicon on insulator (FDSOI) and FinFETs, and will transit to gate all-around FETs (GAA-FETs). Different from the planar devices, the FinFETs and GAA-FETs have a 3D channel. The conventional high-&kappa;/metal gate process using sputtering faces conformality difficulty, and all atomic layer deposition (ALD) of gate stack become necessary. This review covers both scientific and technological parts related to the ALD of metal gates including the concept of effect work function, the material selection, the precursors for the deposition, the threshold voltage (Vt) tuning of the metal gate in contact with HfO2/SiO2/Si. The ALD of n-type metal gate will be detailed systematically, based mainly on the authors&rsquo; works in last five years, and the all ALD gate stacks will be proposed for the future generations based on the learning

QTL mapping of leafy heads by genome resequencing in the RIL population of Brassica rapa.

Leaf heads of cabbage (Brassica oleracea), Chinese cabbage (B. rapa), and lettuce (Lactuca sativa) are important vegetables that supply mineral nutrients, crude fiber and vitamins in the human diet. Head size, head shape, head weight, and heading time contribute to yield and quality. In an attempt to investigate genetic basis of leafy head in Chinese cabbage (B. rapa), we took advantage of recent technical advances of genome resequencing to perform quantitative trait locus (QTL) mapping using 150 recombinant inbred lines (RILs) derived from the cross between heading and non-heading Chinese cabbage. The resequenced genomes of the parents uncovered more than 1 million SNPs. Genotyping of RILs using the high-quality SNPs assisted by Hidden Markov Model (HMM) generated a recombination map. The raw genetic map revealed some physical assembly error and missing fragments in the reference genome that reduced the quality of SNP genotyping. By deletion of the genetic markers in which recombination rates higher than 20%, we have obtained a high-quality genetic map with 2209 markers and detected 18 QTLs for 6 head traits, from which 3 candidate genes were selected. These QTLs provide the foundation for study of genetic basis of leafy heads and the other complex traits

<i>BnA.JAZ5</i> Attenuates Drought Tolerance in Rapeseed through Mediation of ABA–JA Crosstalk

Drought stress reduces water availability in plant cells and influences rapeseed yield. Currently, key genetic regulators that contribute to rapeseed response to drought remain largely unexplored, which limits breeding of drought-resistant rapeseed. In this study, we found that Brassica napus JASMONATE ZIM-DOMAIN 5 (BnA.JAZ5), one of the transcriptional repressors functioning in the jasmonate (JA) signaling pathway, was triggered by drought treatment in rapeseed, and drought-susceptibility increased in BnA.JAZ5-overexpressing rapeseed plants as compared to wild-type plants, resulting in a lower survival rate after recovery from dehydration. After recovery for 3 days, 22–40% of p35S::BnA.JAZ5 transgenic plants survived, while approximately 61% of wild-type plants survived. Additionally, seed germination of BnA.JAZ5-overexpressing rapeseed was hyposensitive to abscisic acid (ABA). The germination rate of five transgenic lines was 32~42% under 9 µM ABA treatment, while the germination rate of wild-type plants was 14%. We also found that the average stomatal density of five overexpressing lines was 371~446/mm2, which is higher than that of wild-type (232/mm2) plants under normal conditions. These results indicate that BnA.JAZ5 regulated drought response in an ABA-dependent manner, possibly by affecting stomatal density. Interestingly, methyl jasmonate (MeJA) treatment rescued the ABA-hyposensitive seed germination, revealing crosstalk between JAZ5-meidated JA and the ABA signaling pathway. Taken together, our results suggest that BnA.JAZ5 attenuated drought resistance through the ABA-dependent pathway, which could represent important genetic loci for drought-resistant rapeseed breeding

miR398 Attenuates Heat-Induced Leaf Cell Death via Its Target CSD1 in Chinese Cabbage

Previous research has shown that miR398 contributed to plant thermotolerance by silencing its target gene COPPER/ZINC SUPEROXIDE DISMUTASE1 (CSD1) in Arabidopsis thaliana. However, the phylogenesis of miR398 and CSD1 in Brassica crop and their role in regulating leaf cell death under heat stress remains unexplored. Here, we characterized the homologous genes of miR398a and CSD1 in Brassica rapa ssp. pekinensis (Chinese cabbage) and found miR398a abundance was accumulated under heat stress (38 °C and 46 °C for 1 h) in Chinese cabbage, while the expression level of its targets BraCSD1-1 and BraCSD2-1 were downregulated. To further explore their role in heat response, we constructed the transgenic plants overexpressing artificial miR398a (aBra-miR398a), Bra-miR398a target mimic (Bra-MIM398a), and BraCSD1-1 in Chinese cabbage for genetic study. Under high temperatures, p35S::aBra-miR398a lines reduced the areas of leaf cell death and delayed the leaf cell death. By contrast, p35S::Bra-MIM398a and p35S::BraCSD1-1 plants enlarged the areas of leaf cell death and displayed the earliness of leaf cell death. Finally, we found that the expression level of stress-responsive genes BraLEA76, BraCaM1, BraPLC, BraDREB2A, and BraP5CS increased in transgenic plants overexpressing aBra-miR398a, which may contribute to their resistance to heat-induced leaf cell death. Taken together, these results revealed the function of Bra-miR398a in attenuating leaf cell death to ensure plant thermotolerance, indicating that the miR398-CSD1 module could be potential candidates for heat-resistant crop breeding