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Nucleation and Growth of the HfO<sub>2</sub> Dielectric Layer for Graphene-Based Devices
Oh, Il-Kwon,Tanskanen, Jukka,Jung, Hanearl,Kim, Kangsik,Lee, Mi Jin,Lee, Zonghoon,Lee, Seoung-Ki,Ahn, Jong-Hyun,Lee, Chang Wan,Kim, Kwanpyo,Kim, Hyungjun,Lee, Han-Bo-Ram American Chemical Society 2015 Chemistry of materials Vol.27 No.17
<P>We investigated nucleation and growth characteristics of atomic layer deposition (ALD) HfO<SUB>2</SUB> on exfoliated and chemical vapor deposition (CVD) graphene by using two Hf precursors, tetrakis(dimethylamino)hafnium (TDMAH) and hafnium tetrachloride (HfCl<SUB>4</SUB>). Experimental results and theoretical calculations indicate that HfO<SUB>2</SUB> nucleation is more favorable on CVD graphene than on exfoliated graphene due to the existence of defect sites. Also, the TDMAH precursor showed much more unfavorable nucleation and growth than HfCl<SUB>4</SUB> due to different initial adsorption mechanisms, affecting lower leakage currents and breakdown electric field. ALD growth characteristics of HfO<SUB>2</SUB> will be fundamentally and practically significant for realizing the fabrication of graphene-based electronic devices.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/cmatex/2015/cmatex.2015.27.issue-17/acs.chemmater.5b01226/production/images/medium/cm-2015-01226v_0007.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/cm5b01226'>ACS Electronic Supporting Info</A></P>
Genome Sequence of <i>Striga asiatica</i> Provides Insight into the Evolution of Plant Parasitism
Yoshida, Satoko,Kim, Seungill,Wafula, Eric K.,Tanskanen, Jaakko,Kim, Yong-Min,Honaas, Loren,Yang, Zhenzhen,Spallek, Thomas,Conn, Caitlin E.,Ichihashi, Yasunori,Cheong, Kyeongchae,Cui, Songkui,Der, Jos Elsevier 2019 Current biology Vol.29 No.18
<P><B>Summary</B></P> <P>Parasitic plants in the genus <I>Striga</I>, commonly known as witchweeds, cause major crop losses in sub-Saharan Africa and pose a threat to agriculture worldwide. An understanding of <I>Striga</I> parasite biology, which could lead to agricultural solutions, has been hampered by the lack of genome information. Here, we report the draft genome sequence of <I>Striga asiatica</I> with 34,577 predicted protein-coding genes, which reflects gene family contractions and expansions that are consistent with a three-phase model of parasitic plant genome evolution. <I>Striga</I> seeds germinate in response to host-derived strigolactones (SLs) and then develop a specialized penetration structure, the haustorium, to invade the host root. A family of SL receptors has undergone a striking expansion, suggesting a molecular basis for the evolution of broad host range among <I>Striga</I> spp. We found that genes involved in lateral root development in non-parasitic model species are coordinately induced during haustorium development in <I>Striga</I>, suggesting a pathway that was partly co-opted during the evolution of the haustorium. In addition, we found evidence for horizontal transfer of host genes as well as retrotransposons, indicating gene flow to <I>S. asiatica</I> from hosts. Our results provide valuable insights into the evolution of parasitism and a key resource for the future development of <I>Striga</I> control strategies.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The <I>Striga</I> genome reflects a three-phase model of parasitic plant genome evolution </LI> <LI> A family of strigolactone receptors has undergone a striking expansion in <I>Striga</I> </LI> <LI> Genes in lateral root development are coordinately induced in a parasitic organ </LI> <LI> Host genes and retrotransposons are horizontally transferred into <I>Striga</I> </LI> </UL> </P>
Area-selective chemical vapor deposition of Co for Cu capping layer
Ryu, S.W.,Kim, S.,Yoon, J.,Tanskanen, J.T.,Kim, H.,Lee, H.B.R. Elsevier 2016 Current Applied Physics Vol.16 No.1
<P>Selective chemical vapor deposition (CVD) of Co on Cu interconnect lines is an advantageous method because it can simplify unit process and suppress side effects resulting from the metal etching process. Density functional theory calculations show that CoCp(CO)(2) has a relatively higher kinetic barrier (36.2 kcal/mol) on SiO2 than that of Co-2(CO)(8) (22.9 kcal/mol). This indicates that CoCp(CO)(2) could be a promising candidate as a Co precursor for selective CVD. Selective CVD of Co films is demonstrated experimentally by deposition on SiO2 and Cu substrates at 200 and 300 degrees C. To reduce C contents in the deposited film, a NH3 plasma process is adopted into conventional CVD in a cyclic CVD process. This process enables deposition of Co films with lower C content while maintaining selective deposition. (C) 2015 Elsevier B.V. All rights reserved.</P>
Oh, Il-Kwon,Park, Bo-Eun,Seo, Seunggi,Yeo, Byung Chul,Tanskanen, Jukka,Lee, Han-Bo-Ram,Kim, Woo-Hee,Kim, Hyungjun The Royal Society of Chemistry 2018 Journal of Materials Chemistry C Vol.6 No.27
<P>Downscaling of complementary metal-oxide semiconductor (CMOS) gate stacks requires the introduction of ultra-thin and high-<I>k</I> dielectrics such as HfO2. Atomic layer deposition (ALD) is an excellent technique for producing high-quality high-<I>k</I> films. During ALD, chemical reactions on the substrate surface involve multiple processes that affect the chemical and electrical properties of the deposited films. Thus, the choice of an appropriate precursor for ALD is critical for obtaining high-quality high-<I>k</I> films, leading to good device performance. The aim of this study is to understand the surface reactions during the film growth along with the evaluation of the electrical properties of HfO2 deposited using two different Hf precursors, HfCl4 and Hf(N(CH3)2)4. The growth behavior and electrical performance of ALD HfO2 thin films obtained using the two Hf precursors and H2O as an oxidant at 250 °C are studied comparatively and discussed as a function of the process parameters, together with surface-reaction energetics determined by the density functional theory. Compared to Hf(N(CH3)2)4, the HfCl4 shows unfavorable nucleation behavior on the starting Si-OH surfaces. In addition, a more stoichiometric HfO2 film results from HfCl4 owing to its high reactivity, leading to lower leakage currents of Si-based devices than that of the film obtained from Hf(N(CH3)2)4. Further, HfCl4 showed better nucleation on a 2D graphene substrate, leading to superior electrical performance in graphene-based field effect transistors. These results provide practical insights on selecting a suitable Hf precursor for producing gate dielectric layers for future nanoelectronics.</P>
Area-selective chemical vapor deposition of Co for Cu capping layer
Seung Wook Ryu,Soohyeon Kim,Jaehong Yoon,Jukka T. Tanskanen,Hyungjun Kim,Han-Bo-Ram Lee 한국물리학회 2016 Current Applied Physics Vol.16 No.1
Selective chemical vapor deposition (CVD) of Co on Cu interconnect lines is an advantageous method because it can simplify unit process and suppress side effects resulting from the metal etching process. Density functional theory calculations show that CoCp(CO)2 has a relatively higher kinetic barrier (36.2 kcal/mol) on SiO2 than that of Co2(CO)8 (22.9 kcal/mol). This indicates that CoCp(CO)2 could be a promising candidate as a Co precursor for selective CVD. Selective CVD of Co films is demonstrated experimentally by deposition on SiO2 and Cu substrates at 200 and 300 C. To reduce C contents in the deposited film, a NH3 plasma process is adopted into conventional CVD in a cyclic CVD process. This process enables deposition of Co films with lower C content while maintaining selective deposition.
Anna-Maija Tolppanen,Riitta Ahonen,Marjaana Koponen,Piia Lavikainen,Maija Purhonen,Heidi Taipale,Antti Tanskanen,Jari Tiihonen,Miia Tiihonen,Sirpa Hartikainen 대한예방의학회 2016 Journal of Preventive Medicine and Public Health Vol.49 No.2
Objectives: Season of birth, an exogenous indicator of early life environment, has been related to higher risk of adverse psychiatric outcomes but the findings for Alzheimer’s disease (AD) have been inconsistent. We investigated whether the month or season of birth are associated with AD. Methods: A nationwide nested case-control study including all community-dwellers with clinically verified AD diagnosed in 2005 to 2012 (n=70 719) and up to four age- sex- and region of residence-matched controls (n=282 862) residing in Finland. Associations between month and season of birth and AD were studied with conditional logistic regression. Results: Month of birth was not associated with AD (p=0.09). No strong associations were observed with season (p=0.13), although in comparison to winter births (December-February) summer births (June-August) were associated with higher odds of AD (odds ratio, 1.03; 95% confidence interval, 1.00 to 1.05). However, the absolute difference in prevalence in winter births was only 0.5% (prevalence of those born in winter were 31.7% and 32.2% for cases and controls, respectively). Conclusions: Although our findings do not support the hypothesis that season of birth is related to AD/dementia risk, they do not invalidate the developmental origins of health and disease hypothesis in late-life cognition. It is possible that season does not adequately capture the early life circumstances, or that other (postnatal) risk factors such as lifestyle or socioeconomic factors overrule the impact of prenatal and perinatal factors.
Tolppanen, Anna-Maija,Ahonen, Riitta,Koponen, Marjaana,Lavikainen, Piia,Purhonen, Maija,Taipale, Heidi,Tanskanen, Antti,Tiihonen, Jari,Tiihonen, Miia,Hartikainen, Sirpa The Korean Society for Preventive Medicine 2016 Journal of Preventive Medicine and Public Health Vol.49 No.2
Objectives: Season of birth, an exogenous indicator of early life environment, has been related to higher risk of adverse psychiatric outcomes but the findings for Alzheimer's disease (AD) have been inconsistent. We investigated whether the month or season of birth are associated with AD. Methods: A nationwide nested case-control study including all community-dwellers with clinically verified AD diagnosed in 2005 to 2012 (n=70 719) and up to four age- sex- and region of residence-matched controls (n=282 862) residing in Finland. Associations between month and season of birth and AD were studied with conditional logistic regression. Results: Month of birth was not associated with AD (p=0.09). No strong associations were observed with season (p=0.13), although in comparison to winter births (December-February) summer births (June-August) were associated with higher odds of AD (odds ratio, 1.03; 95% confidence interval, 1.00 to 1.05). However, the absolute difference in prevalence in winter births was only 0.5% (prevalence of those born in winter were 31.7% and 32.2% for cases and controls, respectively). Conclusions: Although our findings do not support the hypothesis that season of birth is related to AD/dementia risk, they do not invalidate the developmental origins of health and disease hypothesis in late-life cognition. It is possible that season does not adequately capture the early life circumstances, or that other (postnatal) risk factors such as lifestyle or socioeconomic factors overrule the impact of prenatal and perinatal factors.