Ultrafast growth of wafer-scale fold-free bilayer graphene

Bilayer graphene provides a versatile platform for exploring a variety of intriguing phenomena and shows much promise for applications in electronics,optoelectronics,etc.Controlled growth of large-area bilayer graphene is therefore highly desired yet still suffers from a slow growth rate and poor layer uniformity.Meanwhile,graphene wrinkles,including folds and ripples,form during cooling due to the thermal contraction mismatch between graphene and the metal substrates,and have been far from suppressed or eliminated,especially in bilayer graphene,which would greatly degrade the extraordinary properties of graphene.Here we report the ultrafast growth of wafer-scale fold-free bilayer graphene by chemical vapor deposition.Through well-tuning the alloy thickness and strain regulation of the single-crystal CuNi(111)/sapphire,the full coverage of a 2-inch fold-free bilayer graphene wafer via mainly isothermal segregation has been achieved as fast as 30 s.The tensile-strained CuNi(111)film reduces the thermal contraction mismatch and suppresses the formation of graphene folds during cooling,which is directly observed through in situ optical microscopy.The ultraflat bilayer graphene exhibits wafer-scale uniformity in electrical performance and enhanced mechanical property comparable to the exfoliated ones.Our results offer a promising route for largescale production of bilayer graphene and enable its various applications.

Iodine-assisted ultrafast growth of high-quality monolayer MoS_(2) with sulfur-terminated edges

Two-dimensional(2D)semiconductors have attracted great attention to extend Moore’s law,which motivates the quest for fast growth of high-quality materials.However,taking MoS_(2) as an example,current methods yield 2D MoS_(2) with a low growth rate and poor quality with vacancy concentrations three to five orders of magnitude higher than silicon and other commercial semiconductors.Here,we develop a strategy of using an intermediate product of iodine as a transport agent to carry metal precursors efficiently for ultrafast growth of high-quality MoS_(2).The grown MoS_(2) has the lowest density of sulfur vacancies(~1.41×10^(12) cm^(−2))reported so far and excellent electrical properties with high on/off current ratios of 108 and carrier mobility of 175 cm^(2) V^(−1) s^(−1).Theoretical calculations show that by incorporating iodine,the nucleation barrier of MoS_(2) growth with sulfur-terminated edges reduces dramatically.The sufficient supply of precursor and low nucleation energy together boost the ultrafast growth of sub-millimeter MoS_(2) domains within seconds.This work provides an effective method for the ultrafast growth of 2D semiconductors with high quality,which will promote their applications.

Ultrafast growth of high-quality large-sized GaSe crystals by liquid metal promoter

Growth of high-quality large-sized crystals using the traditional chemical vapor transport(CVT)or vertical Bridgman(VB)technique is costly and time-consuming,limiting its practical industrial application.Here,we propose an ultrafast crystal growth process with low energy consumption and capability of producing crystals of excellent quality,and demonstrate that large-sized GaSe crystals with a lateral size of 0.5 to 1 cm can be obtained within a short period of 5 min.X-ray diffraction(XRD)and scanning transmission electron microscopy(STEM)studies clearly indicate that the as-grown crystals have a good crystallinity.To further show the potential application of the resulting GaSe crystals,we fabricate the few-layer GaSe-based photodetector,which exhibits low dark current of 21 pA and fast response of 34 ms under 405 nm illumination.Our proposed technique for rapid crystal growth could be further extended to other metallenes with low-melting point,such as Bi-,Sn-,In-,Pb-based crystals,opening up a new avenue in fulfilling diverse potential optoelectronics applications of two-dimensional(2D)crystals.

Scalable and ultrafast epitaxial growth of single-crystal graphene wafers for electrically tunable liquid-crystal microlens arrays

The scalable growth of wafer-sized single-crystal graphene in an energy-efficient manner and compatible with wafer process is critical for the killer applications of graphene in high-performance electronics and optoelectronics. Here, ultrafast epitaxial growth of single-crystal graphene wafers is realized on singlecrystal Cu90Ni10(1 1 1) thin films fabricated by a tailored two-step magnetron sputtering and recrystallization process. The minor nickel(Ni) content greatly enhances the catalytic activity of Cu, rendering the growth of a 4 in. single-crystal monolayer graphene wafer in 10 min on Cu90Ni10(1 1 1), 50 folds faster than graphene growth on Cu(1 1 1). Through the carbon isotope labeling experiments, graphene growth on Cu90Ni10(1 1 1) is proved to be exclusively surface-reaction dominated, which is ascribed to the Cu surface enrichment in the Cu Ni alloy, as indicated by element in-depth profile. One of the best benefits of our protocol is the compatibility with wafer process and excellent scalability. A pilot-scale chemical vapor deposition(CVD) system is designed and built for the mass production of single-crystal graphene wafers, with productivity of 25 pieces in one process cycle. Furthermore, we demonstrate the application of single-crystal graphene in electrically controlled liquid-crystal microlens arrays(LCMLA), which exhibit highly tunable focal lengths near 2 mm under small driving voltages. By integration of the graphene based LCMLA and a CMOS sensor, a prototype camera is proposed that is available for simultaneous light-field and light intensity imaging. The single-crystal graphene wafers could hold great promising for highperformance electronics and optoelectronics that are compatible with wafer process.

超快激光调控晶体形核与生长过程研究进展

物质的结晶在生物制药、大分子结构分析等领域有着重要的应用,这些应用对结晶结果(包括晶体数量、大小、晶型等)提出了一定的需求,而通过蒸发溶剂或改变温度使溶质析出结晶的传统方法,存在结晶结果难以控制的问题。近年来,超快激光在调控晶体形核生长中的应用得到了关注和研究。超快激光以其超快、超强的特点,在调控晶体形核与生长方面具有独特的作用,且具有热影响区域小、适用材料范围广等优势。本文综述了超快激光调控晶体形核生长过程的研究进展,主要包括超快激光诱导结晶形核、控制晶体生长过程以及晶面图案化加工三个方面,并对超快激光调控晶体形核生长研究的应用前景进行了展望。