More Like this

1. Novel wet transfer technology of manufacturing flexible suspended two-dimensional material devices

   https://doi.org/10.1116/6.0003087  

   Wang, Yingtao; Savalia, Mona; Zhang, Xian (December 2023, Journal of Vacuum Science & Technology B)

   With the rise of two-dimensional (2D) materials, their excellent optical, electronic, and thermal properties different from bulk materials make them increasingly widely studied and commercialized. 2D materials’ exceptional physical properties and unique structures make them an ideal candidate for next-generation flexible and wearable devices. In this work, we created a manufacturing method to successfully transfer monolayer, bilayer, and trilayer graphene onto the flexible substrate, with trenches of micron size to suspend graphene. Thermal transport measurements have been characterized to prove the suspended region. The achievement of manufacturing 2D materials in suspended condition will allow us to study their intrinsic physical properties at a mechanical strain, as well as contribute to novel flexible and wearable electronic devices and sensors. 

   more » « less
2. Epitaxial Oxides on Semiconductors: From Fundamentals to New Devices

   https://doi.org/10.1002/adfm.201901597  

   Kumah, Divine_P; Ngai, Joseph_H; Kornblum, Lior (July 2019, Advanced Functional Materials)

   Abstract Functional oxides are an untapped resource for futuristic devices and functionalities. These functionalities can range from high temperature superconductivity to multiferroicity and novel catalytic schemes. The most prominent route for transforming these ideas from a single device in the lab to practical technologies is by integration with semiconductors. Moreover, coupling oxides with semiconductors can herald new and unexpected functionalities that exist in neither of the individual materials. Therefore, oxide epitaxy on semiconductors provides a materials platform for novel device technologies. As oxides and semiconductors exhibit properties that are complementary to one another, epitaxial heterostructures comprised of the two are uniquely poised to deliver rich functionalities. This review discusses recent advancements in the growth of epitaxial oxides on semiconductors, and the electronic and physical structure of their interfaces. Leaning on these fundamentals and practicalities, the material behavior and functionality of semiconductor–oxide heterostructures is discussed, and their potential as device building blocks is highlighted. The culmination of this discussion is a review of recent advances in the development of prototype devices based on semiconductor–oxide heterostructures, in areas ranging from silicon photonics to photocatalysis. This overview is intended to stimulate ideas for new concepts of functional devices and lay the groundwork for their realization. 

   more » « less
3. Analytical realization of complex thermal meta-devices

   https://doi.org/10.1038/s41467-024-49630-1  

   Li, Weichen; Sigmund, Ole; Zhang, Xiaojia_Shelly (July 2024, Nature Communications)

   Abstract Fourier’s law dictates that heat flows from warm to cold. Nevertheless, devices can be tailored to cloak obstacles or even reverse the heat flow. Mathematical transformation yields closed-form equations for graded, highly anisotropic thermal metamaterial distributions needed for obtaining such functionalities. For simple geometries, devices can be realized by regular conductor distributions; however, for complex geometries, physical realizations have so far been challenging, and sub-optimal solutions have been obtained by expensive numerical approaches. Here we suggest a straightforward and highly efficient analytical de-homogenization approach that uses optimal multi-rank laminates to provide closed-form solutions for any imaginable thermal manipulation device. We create thermal cloaks, rotators, and concentrators in complex domains with close-to-optimal performance and esthetic elegance. The devices are fabricated using metal 3D printing, and their omnidirectional thermal functionalities are investigated numerically and validated experimentally. The analytical approach enables next-generation free-form thermal meta-devices with efficient synthesis, near-optimal performance, and concise patterns. 

   more » « less
4. Advances in complex oxide quantum materials through new approaches to molecular beam epitaxy

   https://doi.org/10.1088/1361-6463/ad2569  

   Rimal, Gaurab; Comes, Ryan B. (February 2024, Journal of Physics D: Applied Physics)

   Abstract Molecular beam epitaxy (MBE), a workhorse of the semiconductor industry, has progressed rapidly in the last few decades in the development of novel materials. Recent developments in condensed matter and materials physics have seen the rise of many novel quantum materials that require ultra-clean and high-quality samples for fundamental studies and applications. Novel oxide-based quantum materials synthesized using MBE have advanced the development of the field and materials. In this review, we discuss the recent progress in new MBE techniques that have enabled synthesis of complex oxides that exhibit ‘quantum’ phenomena, including superconductivity and topological electronic states. We show how these techniques have produced breakthroughs in the synthesis of 4d and 5d oxide films and heterostructures that are of particular interest as quantum materials. These new techniques in MBE offer a bright future for the synthesis of ultra-high quality oxide quantum materials. 

   more » « less
5. Thermal transport in graphene under large mechanical strains

   https://doi.org/10.1063/5.0223188  

   Wang, Yingtao; Zhang, Xian (August 2024, Journal of Applied Physics)

   Flexible electronic devices with skin-like properties are hailed as revolutionary for the development of next-generation electronic devices, such as electric-skin and humanoid robotics. Graphene is intrinsically flexible due to its structural thinness in nature and are considered next-generation materials for wearable electronics. These devices usually experience a large mechanical deformation in use so as to achieve intimate conformal contact with human skin and to coordinate complex human motions, while heat dissipation has been a major limitation when the device is under a large mechanical strain. Unlike the small deformation (<1%) induced by intrinsic material factors such as lattice mismatch between material components in devices, a large mechanical deformation (>1%) by an external loading condition could lead to apparent changes to global geometric shapes and significantly impact thermal transport. In this study, we investigated the thermal conductivities of graphene under several large mechanical strains: 2.9%, 4.3%, and 6.1%. We used a refined opto-thermal Raman technique to characterize the thermal transport properties and discovered the thermal conductivities to be 2092 ± 502, 972 ± 87, 348 ± 52, and 97 ± 13 W/(m K) for the relaxed state, 2.9%, 4.3%, and 6.1% tensile strain, respectively. Our results showed a significant decreasing trend in thermal conductivities with an increasing mechanical strain. The findings in this study reveal new thermal transport mechanisms in 2D materials and shed light on building novel flexible nanoelectronic devices with enhanced thermal management. 

   more » « less