Periodic Reporting for period 1 - WHITEMAG (Engineering magnetic properties of hexagonal boron nitride - based hybrid nanoarchitectures)
Berichtszeitraum: 2020-06-01 bis 2022-05-31
Beyond graphene, a wide variety of other 2D materials have been discovered after the isolation of graphene in 2004, being hexagonal boron nitride (hBN) and borophene two particularly interesting examples because of their complementary properties. Made of alternating boron and nitrogen, hBN owes excellent chemical stability but cannot be used as a switching unit in electronics because of its large band-gap, while borophene, made of boron, is an outstanding conductor but degrades easily. Therefore, it is imperative to investigate new ways to engineer their properties in order to overcome their limitations while exploiting their superb characteristics.
The study of low-dimensional materials, like hBN and borophene, lies at the frontier between materials science, condensed matter physics and physical chemistry. Therefore, the outcome of such interdisciplinary studies are meant to contribute to both basic research and technological applications. In particular, WHITEMAG has been able to provide fundamental insight into the intimate relations between hBN and borophene when synthesized together, into doping mechanism of boron atoms in 2D materials and into relevant molecular processes confined into two dimensions. The results have been reported in prestigious scientific journals, and are expected to inform and enhance publications in diverse fields in the coming years. On the other hand, novel synthesis methods of borophene developed during the action are now in the process of being patented, and are expected to have a direct impact into the growing industry around 2D materials.
The main objectives of the WHITEMAG project consist on tailoring the properties of hBN and borophene by (i) creating nanoarchitectures that combine their complementary properties, (ii) developing innovative growth processes, (iii) heteroatom doping or (iv) incorporation of small molecules. The underlying idea is to exploit their properties so that they can become functional materials valuable for a manifold of applications in fields as diverse as nano-electronics, memory storage, gas sensing or catalysis.
The study of low-dimensional materials, like hBN and borophene, lies at the frontier between materials science, condensed matter physics and physical chemistry. Therefore, the outcome of such interdisciplinary studies are meant to contribute to both basic research and technological applications. In particular, WHITEMAG has been able to provide fundamental insight into the intimate relations between hBN and borophene when synthesized together, into doping mechanism of boron atoms in 2D materials and into relevant molecular processes confined into two dimensions. The results have been reported in prestigious scientific journals, and are expected to inform and enhance publications in diverse fields in the coming years. On the other hand, novel synthesis methods of borophene developed during the action are now in the process of being patented, and are expected to have a direct impact into the growing industry around 2D materials.
The main objectives of the WHITEMAG project consist on tailoring the properties of hBN and borophene by (i) creating nanoarchitectures that combine their complementary properties, (ii) developing innovative growth processes, (iii) heteroatom doping or (iv) incorporation of small molecules. The underlying idea is to exploit their properties so that they can become functional materials valuable for a manifold of applications in fields as diverse as nano-electronics, memory storage, gas sensing or catalysis.
In an initial stage, the synthesis of hBN was achieved on Ir(111) and Cu(111) via chemical vapor deposition (CVD) of borazine. In parallel, the Fellow and co-workers realized that diborane, originating from byproducts of borazine, can be used to grow high-quality borophene on Ir(111). That represented a breakthrough in the field of 2D materials growth, as it was the first time for an elemental atomically-thin material beyond graphene to be grown by CVD. Consequently, and in order to maximize the outcome of the action, efforts were redirected to comprehensively study borophene's properties, and to exploit the newly-developed CVD method for the growth and functionalization of 2D materials beyond the initially proposed hBN.
Thereafter, the diborane-based CVD method was used to synthesize borophene on Cu(111), and diverse nanoarchitectures formed by borophene and hBN. In particular, lateral heterostructures in which borophene and hBN form atomically precise interfaces, and vertical van der Waals heterostructures in which hBN covers borophene and protects it from immediate oxidation. The Fellow characterized the novel heterostructures by techniques with atomic precision (scanning tunneling microscopy and spectroscopy) and surface-average sensitivity (low energy electron diffraction and x-ray photoelectron spectroscopy), which provided insight into the structural, electronic and chemical properties of the novel heterostructures. This part of the action led to the publication of a research article in Science Advances, filing of a patent, several presentations in front of national and international audiences, and the defence of a MSc theses.
In parallel, the potential of hBN to support the fabrication of ordered structures at the nanoscale, inspired by the strong tradition of the host group in this sort of studies. Specifically, hBN was synthesized by CVD of borazine on Ir(100), finding that it naturally develops a moiré corrugation of unconventional 2-fold symmetry. Interestingly, the Fellow and co-workers showed that this can be used to template the self-assembly and orientation of small organic molecules. It was demonstrated for the case of archetypal pentacene, and characterized by the techniques mentioned above, complemented by a photoemission tomography study performed using synchrotron radiation. This part of the action led to the preparation of a manuscript, and the defence of a MSc theses.
In pursuit of creating novel functional nanoarchitectures made of 2D materials, CVD of borane tetrahydrofuran on Ir(111) was explored in the later stages of the action. This was shown to be a successful strategy to fabricate 2D arrays of boron substitutional heteroatoms embedded in an exemplary 2D material like graphene. Through a combined experimental and theoretical effort, the Fellow and collaborators provided a complete description and rationalization of the heteroatom distribution, bonding configurations, interfacial interaction with Ir(111) and impact on graphene's electronic properties. The investigations carried in this last part of the action were summarized in a research article.
Thereafter, the diborane-based CVD method was used to synthesize borophene on Cu(111), and diverse nanoarchitectures formed by borophene and hBN. In particular, lateral heterostructures in which borophene and hBN form atomically precise interfaces, and vertical van der Waals heterostructures in which hBN covers borophene and protects it from immediate oxidation. The Fellow characterized the novel heterostructures by techniques with atomic precision (scanning tunneling microscopy and spectroscopy) and surface-average sensitivity (low energy electron diffraction and x-ray photoelectron spectroscopy), which provided insight into the structural, electronic and chemical properties of the novel heterostructures. This part of the action led to the publication of a research article in Science Advances, filing of a patent, several presentations in front of national and international audiences, and the defence of a MSc theses.
In parallel, the potential of hBN to support the fabrication of ordered structures at the nanoscale, inspired by the strong tradition of the host group in this sort of studies. Specifically, hBN was synthesized by CVD of borazine on Ir(100), finding that it naturally develops a moiré corrugation of unconventional 2-fold symmetry. Interestingly, the Fellow and co-workers showed that this can be used to template the self-assembly and orientation of small organic molecules. It was demonstrated for the case of archetypal pentacene, and characterized by the techniques mentioned above, complemented by a photoemission tomography study performed using synchrotron radiation. This part of the action led to the preparation of a manuscript, and the defence of a MSc theses.
In pursuit of creating novel functional nanoarchitectures made of 2D materials, CVD of borane tetrahydrofuran on Ir(111) was explored in the later stages of the action. This was shown to be a successful strategy to fabricate 2D arrays of boron substitutional heteroatoms embedded in an exemplary 2D material like graphene. Through a combined experimental and theoretical effort, the Fellow and collaborators provided a complete description and rationalization of the heteroatom distribution, bonding configurations, interfacial interaction with Ir(111) and impact on graphene's electronic properties. The investigations carried in this last part of the action were summarized in a research article.
This MSCA action pushed the frontiers of the European Research Area in the fields of 2D materials growth and functionalization in numerous ways. The first CVD route to synthesize an elemental atomically-thin material beyond graphene was established. This allows the scalable synthesis of large single-crystalline flakes of borophene on multiple supports, hence representing a milestone that is meant to have a profound impact in both basic research and industrial applications. First, it unlocks the study of borophene's fundamental properties beyond non-local techniques, and second, it paves the way for its incorporation into nano-electronics, energy storage and gas sensing devices.
Fabrication and study of novel functional nanoarchitectures combining 2D materials with each other or with extrinsic species like heteroatoms or small organic molecules was also achieved. The new CVD route allowed to combine borophene with hBN forming vertical and lateral heterostructures. The vertical van der Waals heterostructure improves borophene's stability against oxidation, while the lateral heterostructure formed by an insulating and a conducting 2D material bonded with atomic precision opens promising prospects for the design of low-power nano-electronics.
Naturally-occurring moiré superstructures in metal-supported 2D materials were shown to template the assembly of organic molecules and heteroatoms in innovative ways. First, the 2-fold superstructure formed in hBN/Ir(100) was shown to effectively guide the self-assembly and orientation of pentacene molecules, hence allowing the characterization of these molecules by surface-averaged techniques like photoemission tomography. Second, the superstructure formed in graphene/Ir(111) was shown to be an ideal platform to guide the incorporation of substitutional heteroatom species in an ordered manner. As a result graphene is functionalized with 2D arrays of heteroatomic species, which constitutes a highly appealing platform for site-selective manipulation of molecular electronic or magnetic states, and applications in the fields of photo-catalysis or gas sensing.
Fabrication and study of novel functional nanoarchitectures combining 2D materials with each other or with extrinsic species like heteroatoms or small organic molecules was also achieved. The new CVD route allowed to combine borophene with hBN forming vertical and lateral heterostructures. The vertical van der Waals heterostructure improves borophene's stability against oxidation, while the lateral heterostructure formed by an insulating and a conducting 2D material bonded with atomic precision opens promising prospects for the design of low-power nano-electronics.
Naturally-occurring moiré superstructures in metal-supported 2D materials were shown to template the assembly of organic molecules and heteroatoms in innovative ways. First, the 2-fold superstructure formed in hBN/Ir(100) was shown to effectively guide the self-assembly and orientation of pentacene molecules, hence allowing the characterization of these molecules by surface-averaged techniques like photoemission tomography. Second, the superstructure formed in graphene/Ir(111) was shown to be an ideal platform to guide the incorporation of substitutional heteroatom species in an ordered manner. As a result graphene is functionalized with 2D arrays of heteroatomic species, which constitutes a highly appealing platform for site-selective manipulation of molecular electronic or magnetic states, and applications in the fields of photo-catalysis or gas sensing.