MSGID: 1:317/3 64a79529   
   PID: hpt/lnx 1.9.0-cur 2019-01-08   
   TID: hpt/lnx 1.9.0-cur 2019-01-08   
    Researchers grow precise arrays of nanoLEDs    
    A new technique produces perovskite nanocrystals right where they're   
   needed, so the exceedingly delicate materials can be integrated into nanoscale   
   devices.    
      
     Date:   
         July 6, 2023   
     Source:   
         Massachusetts Institute of Technology   
     Summary:   
         A new platform enables researchers to 'grow' halide perovskite   
         nanocrystals with precise control over the location and size   
         of each individual crystal, integrating them into nanoscale   
         light-emitting diodes.   
      
      
         Facebook Twitter Pinterest LinkedIN Email   
      
   ==========================================================================   
   FULL STORY   
   ==========================================================================   
   Halide perovskites are a family of materials that have attracted attention   
   for their superior optoelectronic properties and potential applications   
   in devices such as high-performance solar cells, light-emitting diodes,   
   and lasers.   
      
   These materials have largely been implemented into thin-film or   
   micron-sized device applications. Precisely integrating these materials   
   at the nanoscale could open up even more remarkable applications, like   
   on-chip light sources, photodetectors, and memristors. However, achieving   
   this integration has remained challenging because this delicate material   
   can be damaged by conventional fabrication and patterning techniques.   
      
   To overcome this hurdle, MIT researchers created a technique that   
   allows individual halide perovskite nanocrystals to be grown on-site   
   where needed with precise control over location, to within less than 50   
   nanometers. (A sheet of paper is 100,000 nanometers thick.) The size of   
   the nanocrystals can also be precisely controlled through this technique,   
   which is important because size affects their characteristics. Since   
   the material is grown locally with the desired features, conventional   
   lithographic patterning steps that could introduce damage are not needed.   
      
   The technique is also scalable, versatile, and compatible with   
   conventional fabrication steps, so it can enable the nanocrystals to be   
   integrated into functional nanoscale devices. The researchers used this   
   to fabricate arrays of nanoscale light-emitting diodes (nanoLEDs) --   
   tiny crystals that emit light when electrically activated. Such arrays   
   could have applications in optical communication and computing, lensless   
   microscopes, new types of quantum light sources, and high-density,   
   high-resolution displays for augmented and virtual reality.   
      
   "As our work shows, it is critical to develop new engineering frameworks   
   for integration of nanomaterials into functional nanodevices. By moving   
   past the traditional boundaries of nanofabrication, materials engineering,   
   and device design, these techniques can allow us to manipulate matter   
   at the extreme nanoscale dimensions, helping us realize unconventional   
   device platforms important to addressing emerging technological needs,"   
   says Farnaz Niroui, the EE Landsman Career Development Assistant Professor   
   of Electrical Engineering and Computer Science (EECS), a member of the   
   Research Laboratory of Electronics (RLE), and senior author of a new   
   paper describing the work.   
      
   Niroui's co-authors include lead author Patricia Jastrzebska-Perfect,   
   an EECS graduate student; Weikun "Spencer" Zhu, a graduate student in   
   the Department of Chemical Engineering; Mayuran Saravanapavanantham,   
   Sarah Spector, Roberto Brenes, and Peter Satterthwaite, all EECS   
   graduate students; Zheng Li, an RLE postdoc; and Rajeev Ram, professor   
   of electrical engineering. The research will be published in Nature   
   Communications.   
      
   Tiny crystals, huge challenges Integrating halide perovskites into   
   on-chip nanoscale devices is extremely difficult using conventional   
   nanoscale fabrication techniques. In one approach, a thin film of fragile   
   perovskites may be patterned using lithographic processes, which require   
   solvents that may damage the material. In another approach, smaller   
   crystals are first formed in solution and then picked and placed from   
   solution in the desired pattern.   
      
   "In both cases there is a lack of control, resolution, and integration   
   capability, which limits how the material can be extended to nanodevices,"   
   Niroui says.   
      
   Instead, she and her team developed an approach to "grow" halide   
   perovskite crystals in precise locations directly onto the desired   
   surface where the nanodevice will then be fabricated.   
      
   Core to their process is to localize the solution that is used in the   
   nanocrystal growth. To do so, they create a nanoscale template with   
   small wells that contain the chemical process through which crystals   
   grow. They modify the surface of the template and the inside of the   
   wells, controlling a property known as "wettability" so a solution   
   containing perovskite material won't pool on the template surface and   
   will be confined inside the wells.   
      
   "Now, you have these very small and deterministic reactors within which   
   the material can grow," she says.   
      
   And that is exactly what happens. They apply a solution containing halide   
   perovskite growth material to the template and, as the solvent evaporates,   
   the material grows and forms a tiny crystal in each well.   
      
   A versatile and tunable technique The researchers found that the   
   shape of the wells plays a critical role in controlling the nanocrystal   
   positioning. If square wells are used, due to the influence of nanoscale   
   forces, the crystals have an equal chance of being placed in each of   
   the well's four corners. For some applications, that might be good   
   enough, but for others, it is necessary to have a higher precision in   
   the nanocrystal placement.   
      
   By changing the shape of the well, the researchers were able to engineer   
   these nanoscale forces in such a way that a crystal is preferentially   
   placed in the desired location.   
      
   As the solvent evaporates inside the well, the nanocrystal experiences   
   a pressure gradient that creates a directional force, with the exact   
   direction being determined using the well's asymmetric shape.   
      
   "This allows us to have very high precision, not only in growth, but   
   also in the placement of these nanocrystals," Niroui says.   
      
   They also found they could control the size of the crystal that forms   
   inside a well. Changing the size of the wells to allow more or less   
   growth solution inside generates larger or smaller crystals.   
      
   They demonstrated the effectiveness of their technique by fabricating   
   precise arrays of nanoLEDs. In this approach, each nanocrystal is made   
   into a nanopixel which emits light. These high-density nanoLED arrays   
   could be used for on-chip optical communication and computing, quantum   
   light sources, microscopy, and high-resolution displays for augmented   
   and virtual reality applications.   
      
   In the future, the researchers want to explore more potential applications   
   for these tiny light sources. They also want to test the limits of how   
   small these devices can be, and work to effectively incorporate them   
   into quantum systems.   
      
   Beyond nanoscale light sources, the process also opens up other   
   opportunities for developing halide perovskite-based on-chip nanodevices.   
      
   Their technique also provides an easier way for researchers to study   
   materials at the individual nanocrystal level, which they hope will   
   inspire others to conduct additional studies on these and other unique   
   materials.   
      
   "Studying nanoscale materials through high-throughput methods often   
   requires that the materials are precisely localized and engineered at   
   that scale," Jastrzebska-Perfect adds. "By providing that localized   
   control, our technique can improve how researchers investigate and tune   
   the properties of materials for diverse applications."  This work was   
   supported, in part, by the National Science Foundation and the MIT Center   
   for Quantum Engineering.   
      
       * RELATED_TOPICS   
             o Matter_&_Energy   
                   # Nanotechnology # Materials_Science # Optics # Physics   
                   # Engineering_and_Construction # Civil_Engineering #   
                   Graphene # Engineering   
       * RELATED_TERMS   
             o Gallium o Nanorobotics o Crystal_structure o Supercooling   
             o Global_Positioning_System o Quantum_dot o Scale_model o   
             Scientific_method   
      
   ==========================================================================   
      
    Print   
      
    Email   
      
    Share   
   ==========================================================================   
   ****** 1 ****** ***** 2 ***** **** 3 ****   
   *** 4 *** ** 5 ** Breaking this hour   
   ==========================================================================   
       * First_Snapshots_of_Fermion_Pairs *   
       Why_No_Kangaroos_in_Bali;_No_Tigers_in_Australia   
       * New_Route_for_Treating_Cancer:_Chromosomes *   
       Giant_Stone_Artefacts_Found:_Prehistoric_Tools   
       * Astonishing_Secrets_of_Tunicate_Origins *   
       Most_Distant_Active_Supermassive_Black_Hole *   
       Creative_People_Enjoy_Idle_Time_More_Than_Others   
       * Restoring_Fragile_X_Protein_Production *   
       Earth's_Solid_Metal_Sphere_Is_'Textured' *   
       Elephants_Vary_Their_Dinner_Menu_Day-To-Day   
      
   Trending Topics this week   
   ==========================================================================   
   SPACE_&_TIME Asteroids,_Comets_and_Meteors Big_Bang Jupiter   
   MATTER_&_ENERGY Biochemistry Construction Engineering_and_Construction   
   COMPUTERS_&_MATH Educational_Technology Communications   
   Mathematical_Modeling   
      
      
   ==========================================================================   
      
   Strange & Offbeat   
   ==========================================================================   
   SPACE_&_TIME   
   Quasar_'Clocks'_Show_Universe_Was_Five_Times_Slower_Soon_After_the_Big_Bang   
   First_'Ghost_Particle'_Image_of_Milky_Way   
   Gullies_on_Mars_Could_Have_Been_Formed_by_Recent_Periods_of_Liquid_Meltwater,   
   Study_Suggests MATTER_&_ENERGY Holograms_for_Life:_Improving_IVF_Success   
   Researchers_Create_Highly_Conductive_Metallic_Gel_for_3D_Printing   
   Growing_Bio-Inspired_Polymer_Brains_for_Artificial_Neural_Networks   
   COMPUTERS_&_MATH   
   Number_Cruncher_Calculates_Whether_Whales_Are_Acting_Weirdly   
   AI_Tests_Into_Top_1%_for_Original_Creative_Thinking   
   Displays_Controlled_by_Flexible_Fins_and_Liquid_Droplets_More_Versatile,   
   Efficient_Than_LED_Screens Story Source: Materials provided by   
   Massachusetts_Institute_of_Technology. Original written by Adam   
   Zewe. Note: Content may be edited for style and length.   
      
      
   ==========================================================================   
   Journal Reference:   
      1. Patricia Jastrzebska-Perfect, Weikun Zhu, Mayuran   
      Saravanapavanantham,   
         Zheng Li, Sarah O. Spector, Roberto Brenes, Peter F. Satterthwaite,   
         Rajeev J. Ram, Farnaz Niroui. On-site growth of perovskite   
         nanocrystal arrays for integrated nanodevices. Nature   
         Communications, 2023; 14 (1) DOI: 10.1038/s41467-023-39488-0   
   ==========================================================================   
      
   Link to news story:   
   https://www.sciencedaily.com/releases/2023/07/230706124613.htm   
      
   --- up 1 year, 18 weeks, 3 days, 10 hours, 50 minutes   
    * Origin: -=> Castle Rock BBS <=- Now Husky HPT Powered! (1:317/3)   
   SEEN-BY: 15/0 106/201 114/705 123/120 153/7715 218/700 226/30 227/114   
   SEEN-BY: 229/110 112 113 307 317 400 426 428 470 664 700 291/111 292/854   
   SEEN-BY: 298/25 305/3 317/3 320/219 396/45 5075/35   
   PATH: 317/3 229/426