Tian-Ling Ren

Tsinghua University, Peping, Beijing, China

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Publications (159)216.17 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: Understanding the growth mechanism of graphene layers in chemical vapor deposition (CVD) and their corresponding Raman properties is technologically relevant and of importance for the application of graphene in electronic and optoelectronic devices. Here, we report CVD growth of single-crystal trilayer graphene (TLG) grains on Cu and show that lattice defects at the center of each grain persist throughout the growth, indicating that the adlayers share the same nucleation site with the upper layers and these central defects could also act as a carbon pathway for the growth of a new layer. Statistics shows that ABA, 30-30, 30-AB, and AB-30 make up the major stacking orientations in the CVD-grown TLG, with distinctive Raman 2D characteristics. Surprisingly, a high level of lattice defects results whenever a layer with a twist angle of θ = 30° is found in the multiple stacks of graphene layers.
    ACS Nano 10/2014; · 12.03 Impact Factor
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    ABSTRACT: 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.
    Carbon 08/2014; 75:255–261. · 6.16 Impact Factor
  • Cong Yin, Dan Xie, Jian-long Xu, Tian-ling Ren
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    ABSTRACT: Spin valve giant magnetoresistance (GMR) sensors were prepared by a two-step thinning method combining grind thinning and inductively coupled plasma (ICP) etching together. The fabrication processes of front GMR sensors and backside ICP etching were described in detail. Magnetoresistance ratio of about 4.24% and coercive field of approximately 11 Oe were obtained in a tested bendable GMR sensor. The variations of the magnetic property in GMR sensors were explained mainly from the temperature, ion beam damage and mechanical damage generated by the fabrication process.
    Modern Physics Letters B 05/2014; 28(10). · 0.48 Impact Factor
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    ABSTRACT: Laser scribing is an attractive reduced-graphene-oxide (rGO) growth and pattering technology because the process is low-cost, time-efficient, transfer-free and flexible. Various laser-scribed rGO (LSG) components such as capacitors, gas sensors, and strain sensors have been demonstrated. However, obstacles remain towards practical application of the technology where all the components of a system are fabricated using laser scribing. Memory components, if developed, will substantially broaden the application space of low-cost, flexible electronic systems. For the first time, a low-cost approach to fabricate resistive random access memory (ReRAM) using laser-scribed rGO as the bottom electrode is experimentally demonstrated. The one-step laser scribing technology allows transfer-free rGO synthesis directly on flexible substrates or non-flat substrates. Using this time-efficient laser scribing technology, the patterning of a memory-array area up to 100 cm² can be completed in 25 minutes. Without requiring the photoresist coating for lithography, the surface of patterned rGO remains as clean as its pristine status. Ag/HfOx/LSG ReRAM using laser scribing technology is fabricated in this work. Comprehensive electrical characteristics are presented including forming-free behavior, stable switching, reasonable reliability performance and potential for 2-bit storage per memory cell. The results suggest that laser-scribing technology can potentially produce more cost-effective and time-effective rGO-based circuits and systems for practical applications.
    Nano Letters 05/2014; · 13.03 Impact Factor
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    ABSTRACT: We report the structural and enhanced ferromagnetic properties of Mg doped Bi0.8Ca0.2FeO3 ceramics. Oxygen vacancies are introduced into Bi0.8Ca0.2Fe1−xMgxO3 ceramics doping confirmed by XRD and Raman spectra, which induce a significantly enhanced macroscopic ferromagnetism from antiferromagnetism to ferromagnetism. The enhanced ferromagnetism can be ascribed to the creation of unbalanced Fe3+ spins induced by the collapse of the space modulated cycloidal spin structure and relative long-range coupling mediated by the oxygen vacancies trapped localized electrons. The improved ferromagnetic properties obtained by co-doping demonstrate the possibility of bulk BFO in practical multiferroic applications.
    Materials Letters 05/2014; 122:139–142. · 2.27 Impact Factor
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    ABSTRACT: The human hearing range is from 20 Hz to 20 kHz. However, many animals can hear much higher sound frequencies. Dolphins, especially, have a hearing range up to 300 kHz. To our knowledge, there is no data of a reported wide-band sound frequency earphone to satisfy both humans and animals. Here, we show that graphene earphones, packaged into commercial earphone casings can play sounds ranging from 20 Hz to 1 MHz. By using a one-step laser scribing technology, wafer-scale flexible graphene earphones can be obtained in 25 minutes. Compared with a normal commercial earphone, the graphene earphone has a wider frequency response (100 Hz to 50 kHz) and a three times lower fluctuation ( 10 dB). A non-linear effect exists in the graphene generated sound frequency spectrum. This effect could be explained by the DC bias added to the input sine waves which may induce higher harmonics. Our numerical calculations shows that the sound frequency emitted by graphene could reach up to 1 MHz. In addition, we have demonstrated that a dog wearing the graphene earphone could also be trained and controlled by 35 kHz sound waves. Our results show that graphene could be widely used to produce earphones for both humans and animals.
    ACS Nano 04/2014; · 12.03 Impact Factor
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    ABSTRACT: In this paper, a surface acoustic wave (SAW) biosensor with gold delay area on LiNbO3 substrate detecting DNA sequences is proposed. By well-designed device parameters of the SAW sensor, it achieves a high performance for highly sensitive detection of target DNA. In addition, an effective biological treatment method for DNA immobilization and abundant experimental verification of the sensing effect have made it a reliable device in DNA detection. The loading mass of the probe and target DNA sequences is obtained from the frequency shifts, which are big enough in this work due to an effective biological treatment. The experimental results show that the biosensor has a high sensitivity of 1.2 pg/ml/Hz and high selectivity characteristic is also verified by the few responses of other substances. In combination with wireless transceiver, we develop a wireless receiving and processing system that can directly display the detection results.
    Modern Physics Letters B 02/2014; 28(7). · 0.48 Impact Factor
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    ABSTRACT: In virtue of its superior properties, the graphene-based device has enormous potential to be a supplement or an alternative to the conventional silicon-based device in varies applications. However, the functionality of the graphene devices is still limited due to the restriction of the high cost, the low efficiency and the low quality of the graphene growth and patterning techniques. We proposed a simple one-step laser scribing fabrication method to integrate wafer-scale high-performance graphene-based in-plane transistors, photodetectors, and loudspeakers. The in-plane graphene transistors have a large on/off ratio up to 5.34. And the graphene photodetector arrays were achieved with photo responsivity as high as 0.32 A/W. The graphene loudspeakers realize wide-band sound generation from 1 to 50 kHz. These results demonstrated that the laser scribed graphene could be used for wafer-scale integration of a variety of graphene-based electronic, optoelectronic and electroacoustic devices.
    Scientific Reports 01/2014; 4:3598. · 5.08 Impact Factor
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    ABSTRACT: On-chip stacked-spiral radio-frequency (RF) inductor with vertical nanopowder-magnetic-core was proposed and implemented in standard 0.18 μm six-metal CMOS with a post-CMOS backend process module (i.e., CMOS+). To improve on the prior open-magnetic-circuit-loop structure and thus limited improvement at multi-GHz performance, the non-traditional concept shows vertical magnetic core forming a near closed magnetic loop. The ferrite nanoparticle-magnetic-core reduced magnetic loss to improve L-density to 9 GHz. Results show the proof-of-concept designs greatly increase the inductance, L, by up to 34% and the factor, Q, by 62% over a multi-GHz frequency range.
    Journal of Circuits System and Computers 01/2014; 22(10). · 0.24 Impact Factor
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    ABSTRACT: Recently, two-dimensional materials such as molybdenum disulphide (MoS2) have been demonstrated to realize field effect transistors (FET) with a large current on-off ratio. However, the carrier mobility in backgate MoS2 FET is rather low (typically 0.5-20 cm(2)/V·s). Here, we report a novel field-effect Schottky barrier transistors (FESBT) based on graphene-MoS2 heterojunction (GMH), where the characteristics of high mobility from graphene and high on-off ratio from MoS2 are properly balanced in the novel transistors. Large modulation on the device current (on/off ratio of 10(5)) is achieved by adjusting the backgate (through 300 nm SiO2) voltage to modulate the graphene-MoS2 Schottky barrier. Moreover, the field effective mobility of the FESBT is up to 58.7 cm(2)/V·s. Our theoretical analysis shows that if the thickness of oxide is further reduced, a subthreshold swing (SS) of 40 mV/decade can be maintained within three orders of drain current at room temperature. This provides an opportunity to overcome the limitation of 60 mV/decade for conventional CMOS devices. The FESBT implemented with a high on-off ratio, a relatively high mobility and a low subthreshold promises low-voltage and low-power applications for future electronics.
    Scientific reports. 01/2014; 4:5951.
  • Cong Yin, Dan Xie, Jian-Long Xu, Tian-Ling Ren
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    ABSTRACT: In this paper, crystal and magnetic properties of proton irradiated giant magnetoresistance spin valves (GMR-SVs) were investigated based on Ta/NiFe/CoFe/Cu/CoFe/IrMn/Ta stack. GMR-SVs were fabricated by magnetron sputtering and irradiated by 5 MeV proton energy. After irradiation, the magnetic phase of GMR-SV core structures was not affected distinctly while the crystal structure of Ta changed with the radiation dose and dose rate. Degradation of the saturated magnetization and the magnetoresistance ratio was shown in the proton-irradiated samples from the magnetization hysteresis curves and the magnetoresistance measurements, which was explained from the change in the zero-field resistance and the exchange interaction.
    Modern Physics Letters B 12/2013; 28(4). · 0.48 Impact Factor
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    ABSTRACT: In this work, we fabricate a heterojunction small-signal generator (HSSG) based on a graphene-molybdenum disulfide (MoS2) heterojunction. The HSSG is fundamentally different from any analog device developed previously. The HSSG is composed of two quasi-2D heterojunctions and has three terminals named injector (I), recombinator (R), and generator (G). MoS2 serves as I and G, and graphene works as R in the HSSG. The scale coefficient (β = IG/IR) of the HSSG is 1.14 × 10−4 (VIG, IR = 0.2 V) to 1.95 × 10−4 (VIG, IR = 1 V). The current generated from G could be as low as pA scale, which reveals the good performance of the HSSG.
    Applied Physics Letters 12/2013; 103(26):263506-263506-3. · 3.52 Impact Factor
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    ABSTRACT: An ultra-high sensitivity Surface Acoustic Wave (SAW) biosensor operated in high order mode for DNA sequences detection is proposed. Nanoscale interdigitals are fabricated on LiNbO3 substrate to achieve a high quality factor of over 4000 at about 6.4GHz. The biosensor shows an excellent linear response to the target DNA in the range of 1ng/ml to 1μg/ml and the difference of hybridized single DNA base can be distinguished. An effective DNA immobilization increases the frequency shifts greatly, which also contributes to the high sensitivity of 6.7×10-16g/cm2/Hz.
    Electron Devices Meeting (IEDM), 2013 IEEE International; 12/2013
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    ABSTRACT: In this paper, wafer-scale flexible strain sensors with high-performance are fabricated in one-step laser scribing. The graphene films could be obtained by direct reducing graphene oxide film in a light-scribe DVD burner. Our graphene strain sensor has the gauge factor (GF) of 0.11. In order to enhance the GF further, the graphene micro-ribbon has been used as strain sensor, which has the GF up to 9.49, which is higher than most of the reported that of graphene strain sensors (0.55~6.1). Our devices can meet the needs of specific applications, for example, high GF for low-strain applications and low GF for high deformation applications. Our work indicates that laser scribed flexible graphene strain sensors could be widely used for medical-sensing, bio-sensing, artificial skin and many other areas.
    2013 IEEE International Electron Devices Meeting (IEDM); 12/2013
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    ABSTRACT: Graphene strain sensors have promising prospects of applications in detecting human motion. However, the shortage of graphene growth and patterning techniques has become a challenging issue hindering the application of graphene strain sensors. Therefore, we propose wafer-scale flexible strain sensors with high-performance, which can be fabricated in one-step laser scribing. The graphene films could be obtained by directly reducing graphene oxide film in a Light-Scribe DVD burner. The gauge factor (GF) of the graphene strain sensor (10 mm × 10 mm square) is 0.11. In order to enhance the GF further, graphene micro-ribbons (20 μm width, 0.6 mm long) has been used as strain sensors, of which the GF is up to 9.49. The devices may conform to various application requirements, such as high GF for low-strain applications and low GF for high deformation applications. The work indicates that laser scribed flexible graphene strain sensors could be widely used in medical-sensing, bio-sensing, artificial skin and many other areas.
    Nanoscale 11/2013; · 6.73 Impact Factor
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    ABSTRACT: We report high-frequency surface acoustic wave (SAW) devices with excellent temperature stability using a layered structure consisting of single-crystal LiNbO3 thin film on SiO2/LiNbO3 substrate. SAW devices with a wavelength of 2 μm have been fabricated and several wave modes ranging from ∼1.5 to 2.1 GHz have been obtained. With the SiO2 interlayer providing the temperature compensation and the top single-crystal Z-cut LiNbO3 piezoelectric thin film for acoustic wave excitation, the fabricated SAW devices exhibit excellent temperature coefficients of frequency. Theoretical calculations are presented to elucidate temperature compensation of the proposed layered structure.
    IEEE Electron Device Letters 11/2013; 34(12):1572. · 2.79 Impact Factor
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    Thin Solid Films 11/2013; 548:425. · 1.87 Impact Factor
  • 224th ECS Meeting; 10/2013
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    ABSTRACT: Recently, graphene oxide (GO) super capacitors with ultra-high energy densities have received significant attention. In addition to their use in energy storage, GO capacitors might also have broad applications in renewable energy engineering, such as energy harvesting. Here, a flexible nanogenerator based on GO film is designed. A multilayer structure Al/PI/GO/PI/ITO is made on a flexible PET substrate. The GO nanogenerator could generate a peak voltage of 2 V with a current of 30 nA upon the repetitive application of a 15 N force with a frequency of 1 Hz. Moreover, the output voltage was increased to 34.4 V upon increasing the frequency of force application to 10 Hz. Compared with control samples, embedding GO film with a release structure into the device could significantly enhance the output voltage from 0.1 V to 2.0 V. The mechanism of our nanogenerator can be explained by an electrostatic effect, which is fundamentally different from that of previously reported piezoelectric and triboelectric generators. In this manuscript, we demonstrate flexible nanogenerators with large-area graphene based materials, which may open up new avenues of research with regard to applications in energy harvesting.
    Nanoscale 08/2013; · 6.73 Impact Factor
  • Cong Yin, Ze Jia, Wei-chao Ma, Tian-ling Ren
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    ABSTRACT: The magnetoresistance behavior and the magnetization reversal mode of NiFe/Cu/CoFe/IrMn spin valve giant magnetoresistance (SV-GMR) in nanoscale were investigated experimentally and theoretically by nanosized magnetic simulation methods. Based on the Landau-Lifshitz-Gilbert equation, a model with a special gridding was proposed to calculate the giant magnetoresistance ratio (MR) and investigate the magnetization reversal mode. The relationship between MR and the external magnetic field was obtained and analyzed. Studies into the variation of the magnetization distribution reveal that the magnetization reversal mode, that is, the jump variation mode for NiFe/Cu/CoFe/IrMn, depends greatly on the antiferromagnetic coupling behavior between the pinned layer and the antiferromagnetic layer. It is also found that the switching field is almost linear with the exchange coefficient.
    International Journal of Minerals Metallurgy and Materials 07/2013; 20(7). · 0.48 Impact Factor

Publication Stats

276 Citations
216.17 Total Impact Points

Institutions

  • 1998–2014
    • Tsinghua University
      • • Institute of Microelectronics
      • • Department of Microelectronics and Nanoelectronics
      • • Institute of Microelectron
      Peping, Beijing, China
  • 2013
    • Lawrence Berkeley National Laboratory
      Berkeley, California, United States
  • 2007
    • Princeton University
      Princeton, New Jersey, United States