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A nonvolatile resistive switching random access memory (RRAM) device based on the diamond-like carbon (DLC) films and the inert metal electrodes was demonstrated. A typical unipolar resistive switching (RS) behavior without high voltage “forming process” is observed. It exhibits good scaling-down properties when negligible dependence upon the cell area is observed for VSET and IRESET decreases with the reduction of the cell area, which is suitable for practical nonvolatile memory applications. Investigations on the electron transport characteristics at HRS and LRS indicate that Frenkel–Poole emission and Ohmic Laws dominate the LRS and HRS states, respectively. Based on the conduction mechanism studies, the RS behavior is found to arise from the formation and rupture of conductive sp2-like graphitic filaments originating from the connection of conductive sp2-like carbon bonds in the predominantly sp3-like insulating carbon matrix through the electric field induced dielectric breakdown process and thermal fuse effects.

Multi-layer graphene (MLG) films have been deposited on nickel film employing chemical vapor deposition (CVD) technique and oxygen plasma-based treatment method is introduced to tune the properties of MLG films after the transfer process. A MLG of 32 nm (~ 90 layer) was reduced to 12 nm (~ 30 layer) in 60 s with sheet resistance of 550 Ω/□ and transmittance of 83%. The geometrical dimensions, optical transmittance and sheet resistance evolution of the films during the treatment process are investigated. The method suggested in this paper yields controllability of the MLG film thickness and the electrical and optical properties after the transfer process and device fabrication, which has great potentials for transparent conductive electrode applications.

We report the bipolar resistive switching behaviors of the Al/DLC/W structure. The fabricated device shows good memory performances with high ON/OFF ratio, long data retention time, good endurance and low operation voltage. The formed gas bubbles at the Al surface after repeated SET and RESET operations are found to arise from the oxygen vacancies by the formation of Al 2 O 3 layer at the DLC/Al interface, which is also responsible for the resistive switching behaviors of the device.

Due to the extremely high thermal conductivity and low heat capacity per unit area of graphene, it is possible to fabricate an efficient sound-emitting device based on the thermoacoustic effect with no mechanical vibration. In this paper, the fundamental performance of this new graphene sound-emitting device (G-SED) is investigated in terms of its static behavior. The sound amplitude mapping shows that the G-SED has good sound performance under 0.01 W. The sound frequency spectra measured at different distances and angles show that the G-SED has good sound directivity. It is possible to realize sound wave manipulation by using an array of G-SEDs. The relationship between the temperature of graphene and the sound frequency was investigated by a thermal imaging instrument. The fast transient sound response in real time was recorded by applying 60 μs short time multi-pulses and single-pulse. The stable sound emission at a constant sound pressure amplitude with low noise was observed for continuous operation under a fixed frequency over several hours. Such significant performances in this G-SED indicate broad applications, and shed light on the use of graphene in the field of acoustics.

Recently, manipulating heat transport by phononic devices has received significant attention, in which phonon – a heat pulse through lattice, is used to carry energy. In addition to heat control, the thermal devices might also have broad applications in the renewable energy engineering, such as thermoelectric energy harvesting. Elementary phononic devices such as diode, transistor and logic devices have been theoretically proposed. In this work, we experimentally create a macroscopic scale thermal rectifier based on reduced graphene oxide. Obvious thermal rectification ratio up to 1.21 under 12 K temperature bias has been observed. Moreover, this ratio can be enhanced further by increasing the asymmetric ratio. Collectively, our results raise the exciting prospect that the realization of macroscopic phononic device with large-area graphene based materials is technologically feasible, which may open up important applications in thermal circuits and thermal management.

Graphene has attracted significant attention due to its excellent electrical, optical, mechanical and thermal properties. In the paper, we report a simple and efficient growth method of multilayer graphene using a metal-catalyzed crystallization of diamond-like carbon (DLC) by thermal annealing without any extraneous carbon sources. The Ni/DLC/Si multilayered structure was fabricated on silicon substrate at room temperature (RT) and then was thermally annealed. Multilayer graphene was formed on the nickel surface after cooling down to RT by the analysis of Raman spectra. The quality of the multilayer graphene is comparable to chemical vapor deposition methods (CVD). This method of synthesizing graphene sheets with DLC films provides an important way toward the integration of DLC-based electronic devices with graphene.

Single-layer graphene (SLG) was demonstrated to emit sound. The sound emission from SLG had a significant flat frequency response in the wide ultrasound range from 20 kHz to 50 kHz. SLG can produce a sound pressure level (SPL) as high as 95 dB at a distance of 5 cm with a sound frequency of 20 kHz. The SPL value is among the highest reported to date for sound-emitting devices (SEDs) based on the thermoacoustic effect. A theoretical model was established to analyze the sound emission from SLG. The theoretical results are in good agreement with the experimental results. Conventional acoustic devices with a large size can be reduced to the nano-scale by using this novel SLG-SED material. It has the potential to be widely used in speakers, buzzers, earphones, ultrasonic transducer, etc.

We demonstrate an interesting phenomenon that graphene can emit sound. The application of graphene can be expanded in the acoustic field. Graphene-on-paper sound source devices are made by patterning graphene on paper substrates. Three graphene sheet samples with the thickness of 100, 60, and 20 nm were fabricated. Sound emission from graphene is measured as a function of power, distance, angle, and frequency in the far-field. The theoretical model of air/graphene/paper/PCB board multilayer structure is established to analyze the sound directivity, frequency response, and efficiency. Measured sound pressure level (SPL) and efficiency are in good agreement with theoretical results. It is found that graphene has a significant flat frequency response in the wide ultrasound range 20-50 kHz. In addition, the thinner graphene sheets can produce higher SPL due to its lower heat capacity per unit area (HCPUA). The infrared thermal images reveal that a thermoacoustic effect is the working principle. We find that the sound performance mainly depends on the HCPUA of the conductor and the thermal properties of the substrate. The paper-based graphene sound source devices have highly reliable, flexible, no mechanical vibration, simple structure and high performance characteristics. It could open wide applications in multimedia, consumer electronics, biological, medical, and many other areas.

The structural and electrical characteristics of Metal-Pb(Zr 0.53 Ti 0.47 )O 3 (PZT)-TiO 2 -Si structures with TiO 2 insulating layer deposited by metal organic chemical vapor deposition (MOCVD) method were investigated. The dependence of the electrical performances such as memory window (MW) and leakage current density on the thickness of the insulator layer and electrode material was studied. Highly preferred orientation PZT thin film was obtained on the well crystallized TiO 2 insulator layer. For the Pt/PZT/TiO 2 (190nm)/Si structure working in the charge injection mode, a memory window of 0.5V and 2.2V, and a leakage current density of 3.38×10−7A/cm2, 6.21×10−7A/cm2 were obtained under a sweeping voltage of 5V and 7V, respectively. The memory characteristics suggest the possibility for next generation nonvolatile memory applications.

We report the influences of pulse widths on the programming and erasing characteristics of diamond-like carbon films based resistive random access memory. The device can be only programmed with pulses wider than 50 ns for SET operations when the pulse voltage is 1.2 V and erased with pulses narrower than 25 ns for RESET operations when the pulse voltage is 0.4 V. The formation, rupture, and re-growth of the conductive sp2-like graphitic filaments are proposed to be responsible for the resistive switching behaviors, based on which the pulse widths dependences on its programming and erasing properties can be further explained.

The structural and electrical properties of a metal-ferroelectric-insulator-semiconductor (MFIS) structure with an Al2O3 layer prepared by using the molecular atomic deposition method and Pb(Zr0.52Ti0.48)O3 (PZT) deposited by the radio frequency magnetron sputtering method are investigated. PZT exhibits a very smooth surface and (110) orientation of the perovskite phase. The MFIS structure shows well-behaved clockwise capacitance-voltage hysteresis loops due to the ferroelectric polarization under a sweep voltage up to ±40 V. Memory windows of 1.9 V and 18.14 V in conjunction with leakage current density of 2.42 × 10−7 A/cm2 and 8.28 × 10−7 A/cm2 are obtained under sweep voltages of ±5 V and ±20 V, respectively.

In this paper, nonvolatile bipolar resistive switching (BRS) as well as unipolar resistive switching (URS) effects are observed in diamond-like carbon (DLC) thin films prepared by the filtered cathodic vacuum arc technique. By controlling the current compliance, either bipolar or unipolar switching is obtained. The fabricated Al/DLC/W structure showing BRS exhibits good performance with a low operation voltage (105 s. The mechanism of BRS is fitted by ohmic and SCLC laws in the low resistance state and high resistance state scenarios. Fuse and antifuse effects are proposed to be the principle for the URS behaviour.

In this paper, nonvolatile bipolar resistive memory effects were observed in nitrogen doped diamond-like carbon (DLC) thin films prepared by a pulsed laser deposition technique. It is observed that the fabricated Pt/Ti/DLC/Pt structure exhibits good memory performances with an ON/OFF ratio >10, data retention time >104 s, and low operation voltage (

We demonstrated flexible, ultrathin, and transparent sound-emitting devices (SEDs) using silver nanowires (AgNWs). Large area of AgNWs film on substrate was made by dry transfer technique. The sound emission from the AgNWs was measured as a function of power, distance, and frequency. Significant flat and wide frequency responses occurred between 15 and 45 kHz. The sound pressure was in good agreement with theoretical results. This indicates that a thermoacoustic effect exists in AgNWs. The AgNWs-SEDs can be integrated with the liquid crystal display, which shows the potential to be an important component in flexible electronic systems.

An organic, ultrathin, and transparent sound-emitting device was fabricated using poly(3,4-ethylenedioxythiophene):poly(styrenesulfonic) (PEDOT:PSS) films. This sound-emitting device was easily processed by spin coating. Sound emission from PEDOT:PSS was measured as a function of power, distance, and frequency. The sound frequency spectrum was found to be ultra-flat in a wide sound frequency range (10–45 kHz). Theoretical analysis showed that the working principle was the thermoacoustic effect. The PEDOT:PSS sound-emitting device has potential applications in the acoustic field. In particular, it can be integrated with a liquid crystal display to realize sound emission and image display at the same time.

Thermoacoustic effects were observed in 100-nm indium tin oxide (ITO) films. The sound emission from the ITO films was measured as a function of power, distance, and frequency. Significant flat and wide frequency responses occurred between 20 and 50 kHz. The sound pressure and efficiency were in good agreement with theoretical results. This indicates that a thermoacoustic effect exists in metal-oxide materials and that a large family of transparent electrode materials may exhibit similar properties. Using the ultrathin, transparent, and flexible characteristics, we showed promising applications of ITO sound source devices that were integrated with liquid crystal display screens.