Wafer-scale graphene/ferroelectric hybrid devices for low-voltage electronics (original) (raw)
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Advanced electronic materials, 2017
demonstrated tenfold improvement of charge carrier mobility in graphene-based field-effect transistors (FETs) when a conventional Si/SiO 2 substrate is replaced by an epitaxial lead zirconate titanate Pb(Zr,Ti)O 3 (PZT) film. Several other studies also showed that graphene-based FETs on ferroelectric substrates have nonvolatile memory properties. [3-8] While these studies demonstrate some practical characteristics of graphene-ferroelectric FETs (FeFETs), their electrical properties are not yet completely understood. In particular, these devices exhibit an unusual antihysteresis of electronic transport, which contradicts the hysteretic polarization dependence of PZT. [3-6] The electronic behavior of graphene FeFETs is schematically illustrated by Figure 1.
Advanced Electronic Materials, 2017
demonstrated tenfold improvement of charge carrier mobility in graphene-based field-effect transistors (FETs) when a conventional Si/SiO 2 substrate is replaced by an epitaxial lead zirconate titanate Pb(Zr,Ti)O 3 (PZT) film. Several other studies also showed that graphene-based FETs on ferroelectric substrates have nonvolatile memory properties. [3-8] While these studies demonstrate some practical characteristics of graphene-ferroelectric FETs (FeFETs), their electrical properties are not yet completely understood. In particular, these devices exhibit an unusual antihysteresis of electronic transport, which contradicts the hysteretic polarization dependence of PZT. [3-6] The electronic behavior of graphene FeFETs is schematically illustrated by Figure 1.
arXiv (Cornell University), 2021
While technologically challenging, the integration of ferroelectric thin films with graphene spintronics potentially allows the realization of highly efficient, electrically tuneable, non-volatile memories through control of the interfacial spin-orbit driven interaction occuring at graphene/Co interfaces deposited on heavy metal supports. Here, the integration of ferroelectric Hf0.5Zr0.5O2 on graphene/Co/heavy metal epitaxial stacks is investigated via the implementation of several nucleation methods in atomic layer deposition. By employing in-situ Al2O3 as a nucleation layer sandwiched between Hf0.5Zr0.5O2 and graphene, the Hf0.5Zr0.5O2 demonstrates a remanent polarization (2Pr) of 19.2 µC/cm 2. Using an ex-situ, naturally oxidized sputtered Ta layer for nucleation, 2Pr could be controlled via the interlayer thickness, reaching maximum values of 28 µC/cm 2 with low coercive fields. Magnetic hysteresis measurements taken before and after atomic layer deposition show strong perpendicular magnetic anisotropy, with minimal deviations in the magnetization reversal pathways due to the Hf0.5Zr0.5O2 deposition process, thus pointing to a good preservation of the magnetic stack including single-layer graphene. X-ray diffraction measurements further confirm that the high-quality interfaces demonstrated in the stack remain unperturbed by the ferroelectric deposition and anneal. The proposed graphene-based ferroelectric/magnetic structures offer the strong advantages of ferroelectricity and ferromagnetism at room temperature, enabling the development of novel magneto-electric and non-volatile in-memory spin-orbit logic architectures with low power switching. 1
Synthesis of Wafer-Scale Graphene with Chemical Vapor Deposition for Electronic Device Applications
Advanced Materials Technologies, 2021
Graphene has attracted considerable interest since it was first isolated in 2004. This interest was renewed in 2018 with the breakthrough discovery of "magic-angle" twisted bilayer graphene. [1-3] Since 2018, many novel physical properties have been identified, including superconductivity, [4] many-body correlations, [5] electronic correlations , [6,7] linear-in-temperature resis-tivity, [8] "strange metal" behavior with Planckian dissipation, [9] ferromagnetism, [10] and Mott insulation. [11] Exciton physics [12,13] and valleytronics [14,15] have emerged as relevant research fields. Novel morphologies such as origami graphene [16] have also attracted interest, and nanoporous gra-phene has been earmarked for the filtration and separation of ions and gases. [17,18] The first isolation of graphene opens the avenue for new platforms for physics, electronic engineering, and materials sciences. Among several kinds of synthesis approaches, chemical vapor deposition is most promising for the growth at wafer-scale, which is compatible with the Si-based electronic device integration protocols. In this review, the types, properties, and synthesis methods of graphene are first introduced. Many details of wafer-scale gra-phene synthesis by chemical vapor deposition strategies are given, including the wafer-scale single crystal metal and alloy preparation, roll to roll synthesis over Cu, roll to roll electrochemical transfer technique. Besides, the batch-to-batch synthesis are highlighted for direct graphene over dielectric substrates such as sapphire and Si/SiO 2. The electronic transport and transparent conductance of the wafer-scale graphene are compared with high-quality single crystal. The progress and proof-of-the-concept are briefly recalled in graphene-based electronics such as transistors, sensors, integrated circuits, and spin transport valves. Eventually, the readers are provoked with the current challenges as well as the future opportunities.
Nano Letters, 2010
Graphene is considered to be a promising candidate for future nano-electronics due to its exceptional electronic properties. Unfortunately, the graphene field-effect-transistors (FETs) cannot be turned off effectively due to the absence of a bandgap, leading to an on/off current ratio typically around 5 in top-gated graphene FETs. On the other hand, theoretical investigations and optical measurements suggest that a bandgap up to a few hundred meV can be created by the perpendicular E-field in bi-layer graphenes. Although previous carrier transport measurements in bi-layer graphene transistors did indicate a gate-induced insulating state at temperature below 1 Kelvin, the electrical (or transport) bandgap was estimated to be a few meV, and the room temperature on/off current ratio in bi-layer graphene FETs remains similar to those in single-layer graphene FETs. Here, for the first time, we report an on/off current ratio of around 100 and 2000 at room temperature and 20 K, respectively in our dual-gate bi-layer graphene FETs. We also measured an electrical bandgap of >130 and 80 meV at average electric displacements of 2.2 and 1.3 V/nm, respectively. This demonstration reveals the great potential of bi-layer graphene in applications such as digital electronics, pseudospintronics, terahertz technology, and infrared nanophotonics.
Combining graphene and organic ferroelectric for possible memory devices
Both ferroelectric materials and graphene attract plenty of scientific attention. Ferroelectrics are well known for their ability to maintain a polarization, which can be switched/reversed by an external electric field. Organic ferroelectrics (e.g. PVDF/TrFE) are of special interest because of their flexibility and durability. Graphene has already demonstrated its promise for future electronics. The two materials brought together give a new functionality of non-volatile memory. Proof-of-concept works have been already done, but only with exfoliated graphene. The main goal of this research is to study the possibility of making such devices using CVD graphene, in large amounts. In other words, we address the feasibility of this kind of graphene-based memory devices. This can be important for graphene-based electronics in the near future.
arXiv (Cornell University), 2017
P-N junctions in graphene on ferroelectric have been actively studied, but the impact of piezoelectric effect in ferroelectric substrate with ferroelectric domain walls (FDWs) on graphene characteristics was not considered. Due to the piezo-effect ferroelectric domain stripes with opposite spontaneous polarizations elongate or contract depending on the polarity of voltage applied to the substrate. We show that the alternating piezoelectric displacement of the ferroelectric domain surfaces can lead to the alternate stretching and separation of graphene areas at the steps between elongated and contracted domains. Graphene separation at FDWs induced by piezo-effect can cause unusual effects. In particular, the conductance of graphene channel in a field effect transistor increases essentially, because electrons in the stretched section scatter on acoustic phonons. At the same time the graphene conductance is determined by ferroelectric spontaneous polarization and varies greatly in the presence of FDWs. The revealed piezo-mechanism of graphene conductance control is promising for next generations of graphene-based field effect transistors, modulators, electrical transducers and piezo-resistive elements. Also our results propose the method of suspended graphene fabrication based on piezo-effect in a ferroelectric substrate that does not require any additional technological procedures.
Field-Effect Transistors Based on Single-Layer Graphene and Graphene-Derived Materials
Micromachines
The progress of advanced materials has invoked great interest in promising novel biosensing applications. Field-effect transistors (FETs) are excellent options for biosensing devices due to the variability of the utilized materials and the self-amplifying role of electrical signals. The focus on nanoelectronics and high-performance biosensors has also generated an increasing demand for easy fabrication methods, as well as for economical and revolutionary materials. One of the innovative materials used in biosensing applications is graphene, on account of its remarkable properties, such as high thermal and electrical conductivity, potent mechanical properties, and high surface area to immobilize the receptors in biosensors. Besides graphene, other competing graphene-derived materials (GDMs) have emerged in this field, with comparable properties and improved cost-efficiency and ease of fabrication. In this paper, a comparative experimental study is presented for the first time, for FE...