Single p-type/intrinsic/n-type silicon nanowires as nanoscale avalanche photodetectors

We report the controlled synthesis of axial modulation-doped p-type/intrinsic/n-type (p-i-n) silicon nanowires with uniform diameters and single-crystal structures. The p-i-n nanowires were grown in three sequential steps: in the presence of diborane for the p-type region, in the absence of chemical dopant sources for the middle segment, and in the presence of phosphine for the n-type region. The p-i-n nanowires were structurally characterized by transmission electron microscopy, and the spatially resolved electrical properties of individual nanowires were determined by electrostatic force and scanning gate microscopies. Temperature-dependent current-voltage measurements recorded from individual p-i-n devices show an increase in the breakdown voltage with temperature, characteristic of band-to-band impact ionization, or avalanche breakdown. Spatially resolved photocurrent measurements show that the largest photocurrent is generated at the intrinsic region located between the electrode contacts, with multiplication factors in excess of ca. 30, and demonstrate that single p-i-n nanowires function as avalanche photodiodes. Electron- and hole-initiated avalanche gain measurements performed by localized photoexcitation of the p-type and n-type regions yield multiplication factors of ca. 100 and 20, respectively. These results demonstrate the significant potential of single p-i-n nanowires as nanoscale avalanche photodetectors and open possible opportunities for studying impact ionization of electrons and holes within quasi-one-dimensional semiconductor systems.     

Recent advances in hydrogel-based anti-infective coatings

Bacterial infections associated with biomedical devices and implants have posed a great challenge to global healthcare systems.These infections are mainly caused by bacterial biofilm formed on the surface of biomaterials,protecting the encapsulated bacteria from conventional antibiotic treatment and attack of the immune system.As the bacterial biofilm is difficult to eradicate,bactericidal and antifouling coatings have emerged as promising strategies to prevent biofilm formation and subsequent infections.Hydrogels with three-dimensional crosslinked hydrophilic networks,tunable mechanical property and large drug-loading capacity are desirable coating materials,which can kill bacteria and/or prevent bacterial adhesion on the surface,inhibiting biofilm formation.Herein,we review recent developments of hydrogels as anti-infective coatings.Particularly,we highlight two chemical approaches(graft-from and graft-to),which have been used to immobilize hydrogels on surfaces,and present advances in the development of bactericidal(contact-killing and antimicrobial-releasing),antifouling(hydrophilic polymer network)and bifunctional hydrogel coatings with both bactericidal and antifouling activities.In addition,the challenges of hydrogel coatings for clinical applications are discussed,and future research directions of anti-infective hydrogel coatings are proposed.     

城市窗口 垂直的当代美术馆

设计者选择在曼哈顿的Prince和Browery大街上设计一个垂直的当代美术馆。这一地区作为关键的地理和文化交汇点,孕育了数代艺术家。他们在此生活和工作,为民族文化对话的不断推进贡献自己的力量。     

祁家渡钢管混凝土拱桥的地震反应分析

随着钢管混凝土这种组合材料应用于工程实践,拱桥的跨越能力取得了长足的发展。本文以甘肃在建的主跨180m,宽跨比为1/25.7的上承式钢管混凝土拱桥为例,详细分析了该桥的自振特性,进行了地震响应的反应谱法分析和时程反应分析,并分析了桥面系的弹性约束对主拱结构动力特性的影响。结果表明:由于该桥的宽跨比小于1/20,对长周期地震波的响应较大。     

Relationship between microstructure and tensile properties on a near-β titanium alloy after multidirectional forging and heat treatment

In this study, a new near-beta titanium alloy, Ti-4Al-1Sn-2Zr-5Mo-8V-2.5Cr, was prepared by induction skull melting(ISM) and multidirectional forging. The effect of aging heat treatment on microstructure and tensile properties of the alloy after solution treatment in the twophase(α + β) region was investigated. The micros tructure results show that the globular primary α phase(α_p) and the needle-like secondary α phase(α_s) are precipitated in the β matrix. The size of α_s increases with the increase in aging temperature,while the content of α_s goes up to a peak value and then decreases. The tensile testing results show that the strength increases first and then decreases with the increase in temperature. The variation of ductility presents the opposite way compared with the trend of strength level.When aged at 500 ℃, the alloy exhibits an excellent balance of tensile strength(1529 MPa) and elongation(9.22%). And the relative mechanism of strengthening and toughening was analyzed and discussed.     

PREDICTION OF THERMODYNAMIC PROPERTIES OF THE FeO-CaO-SiO_2 MELTS FROM WILSON EQUATION

1.IntroductionIn0rdert0c0mpensateforash0rtc0ming0fclassicaltherm0dynamics,manyempiricalorsemiempiricalmodelsbased0nthethe0ryofregularsolutionshavebeendevel0pedforpredictingthethermodynamicpr0pertiesofternaryandevenmulticomponentmoltenslags[l'2].Ac0mmoncharacteristic0fthemist0usem0reempiricalappr0aches.Ifonlybinarydataareusedtopredictthetherm0dynamicpr0pertiesofaternarysystem,thedeviationsofpredictedvalueswillbelarger;ifthevauesneedtomatchtherequiredaccuracytaporti0n0fexperimentaldataofaternary…     

HYDROGEN EFFECT ON DEFORMATION BEHMIOR OF TITANIUM ALLOY AT HIGH TEMPERATURE

1.IntroductionContinuousfiberreinforcedtitaniummatrixcompositeshavepotentialapplicationatelevatedtemperature.Anewmethodhajsbeentriedbyoneofthepresentautho.s[1'21toalleviatethedeleteriousinterfacereactionbetweenthefiberandthematrix,whichislikelytooccurinthiscompositeduringfabrication.Previous.orb[llshowedthattitaniummatrixcompositecanachievefullconsolidationatrelativelylowtemperaturewiththeaidofhydrogenasatemporaryalloyingelement.Furtherstudyalongthisdirectionshouldbebasedonacomprehensiveunders…     

ELECTROCHEMICAL PROPERTIES OF Zr V Ni SYSTEM HYDROGEN STORAGE ALLOYS

１ＩＮＴＲＯＤＵＣＴＩＯＮＩｎｔｈｅｂｉｎａｒｙａｌｏｙｓＺｒＭ２（Ｍ＝Ｖ,ＣｒｏｒＭｎ３ｄｔｒａｎｓｉｔｉｏｎｍｅｔａｌ）,ＺｒＶ２ｍａｉｎｌｙｗｉｔｈａＣ１５Ｌａｖｅｓｐｈａｓｅｃａｎａｂｓｏｒｂｔｈｅｈｉｇｈｅｓｔｈｙｄｒｏｇｅｎｃｏｎｔｅｎ...     

THERMAL DEMAGNETIZATION AND RANDOMNESS OF DOMAIN NUCLEATION OF SINGLE PHASE Nd_2 Fe_(14) B

Based on the observation of temperature variation of both domain structure and magnetic con-trast.the thermal demagnetization and randomness of domain nucleation was discussed.