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Wafer-scale synthesis and transfer of monolayer …
The novelty of this work is the integrating of wafer-scale high-performance graphene-based in-plane transistors, photodetectors and loudspeakers with one-step fabrication. The achievements in our work are mainly four parts. Firstly, a laser scribing technology to fabricate wafer-scale grapheme was developed. This laser scribing technology has the advantages of forming graphene in designed shape at precise locations, low cost with large scale fabrication ability and simple process. Secondly, laser scribed graphene was used to realize all graphene-based large-scale in-plane transistors with high Ion/Ioff ratio, this parameter is better than that of most CVD graphene,, (Ion/Ioff ratio ~1.04 ~ 1.4). Thirdly, the large-scale photodetectors and line pixels imaging with high photo responsivity were achieved with the laser scribed graphene. As far as we know, this is the first demonstration 1-dimentional and 2-dimentional array of graphene photodetectors for photo imaging. In addition, the responsivity of photodetectors is 2 orders magnitude, which is much better than that of the reported rGO. Fourthly, the sound generation in a wide range was realize with laser scribed graphene, of which the sound generation spectrum (1–50 kHz) is 2.5 times wider than that of reported mono-layer graphene on PDMS (1–20 kHz).
The acoustic platform for testing laser scribed graphene loudspeakers contained a standard microphone and a dynamic signal analyzer. The 1/4 inch standard microphone (Earthworks M50), which had a very flat frequency response reaching up to 50 kHz and a 31 mV/Pa high sensitivity, was used to measure the sound pressure level of the loudspeakers. The signal analyzer (Agilent 35670A) was used to generate sine signals to drive loudspeakers, make fast Fourier transform analysis and record the value of sound pressure level. Our test results were measured in a soundproof box. The box size is 1 × 0.5 × 0.5 m3. In order to avoid the effects of reflections, the box was filled with sound-absorbing sponges.
Wafer-scale synthesis and transfer of graphene films.
From the discussion above, the wafer-scale direct fabrication of graphene-based transistors, photodetectors and loudspeakers are achieved with a common LightScribe DVD burner. By controlling the pattering times, the resistance of the graphene could be tuned. Laser scribed in-plane graphene transistors have been demonstrated to have a large on/off ratio up to 5.34. Photo responsivity and specific detectivity as high as 0.32 A/W and 4.996 × 1010 cmHz1/2W−1 have been observed in the laser scribed graphene photodetectors. Sound generation of laser scribed graphene is also well demonstrated ranging from 1 to 50 kHz sound frequency. This work indicates that laser scribing technology could be a powerful and efficient method to integrate high-performance graphene-based devices.
The schematic diagrams and experimental results for a laser scribed in-plane graphene transistor are sketched in . The fabrication process for a laser scribed in-plane graphene transistor is depicted in the schematic diagram in . The transfer characteristic for the in-plane graphene transistor with 0.1 V applied bias voltage Vds is indicated in . As seen in the graph, the Ion/Ioff is up to 5.34, which is much higher than that of most CVD graphene transistors,,, and similar to performance of exfoliated graphene,. The transfer curve shows the holes transport with 9.87 cm2V−1s−1 mobility (See detail calculations of the mobility in ). As the structure defects exist in laser scribed graphene, the low mobility could be reasonable and is similar to the reported results. It should be noted that the Dirac point shifts larger than 40 V, which could be explained by the present of residual oxygens those dope the graphene into highly p-type. The frequency dependence of the specific capacitance of the capacitor in graphene/GO in-plane graphene configuration is shown in . As can be seen, the capacitance at 1 kHz frequency is 6.34 × 10−4 Fm−2. The Ids–Vds curve recorded for different values of Vig is shown in . Positive gate voltage could lead to lower current and negative gate voltage makes the current higher, which is consistant with the transfer curve shown in .
Wafer-scale synthesis and transfer of high quality …
Panda, S. K., Lee, S., Yoon, W.-S., and Shin, H., "Reversible phase transformation of titania (anatase) nanotubes upon electrochemical lithium-intercalation observed by ex situ transmission electron microscopy", J. Power Sources, 249, 59-65 (2014)
The scalable fabrication of laser scribed graphene is depicted in . The DVD burner containing light scribe function has been used. The 788 nm laser pulses with 5 mW maximum power produced by the burner could convert the stack single-layer GO film into graphene (). A designed patterning with grayscale, which could control the DVD drive for selective reduction of GO, was import to the software in order to control the patterning position and laser intensity. As shown in , wafer-scale in-plane transistor patterns are designed. After importing the electronic file into the computer software and ~25-minute laser scribing in DVD burner, graphene transistors are directly patterned on a GO film (). shows the logo of Tsinghua University and the corresponding graphene pattern on the GO film (). A colored picture and the corresponding laser scribed graphene patterning gray scale are given in . show an array of graphene transistors, an array of photodetectors, and a graphene loudspeaker device integrated on a flexible substrate by the direct laser scribing method. The wafer-scale fabrication flexible graphene-based devices after peeling off with the PET substrate from the DVD disc is shown in .
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Electrochemical routes for industrial synthesis - SciELO
In this work, the integrated wafer-scale in-plane transistors, the photodetectors and the loudspeakers by laser scribing technology are proposed. This is a substantial novel research study that has several approaches. Firstly, the in-plane graphene transistor has a large on/off ratio up to 5.34. This parameter is much higher than that of most CVD graphene (Ion/Ioff ratio ~1.04 ~ 1.4),,. Secondly, the graphene photodetectors with photo responsivity and specific detectivity as high as 0.32 A/W and 4.996 × 1010 cmHz1/2W−1 under 0.1 V bias were achieved. As far as we know, this is the first demonstration of 1-dimentional and 2-dimentional array of graphene photodetectors for photo imaging. Thirdly, the laser scribed graphene is also demonstrated to be a high performance loudspeaker with wide-band sound generation from 1 to 50 kHz. The sound generation spectrum (1–50 kHz) is 2.5 times wider than that of reported mono-layer graphene on PDMS (1–20 kHz).
22/04/2008 · REVIEW
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.
Electrochemical routes for industrial synthesis
Laser scribing is an attractive pattering technology due to its low-cost and time-efficient fabrication process. The one-step laser scribing technology allows transfer-free graphene synthesis directly on flexible substrates or uneven substrates. In general, CVD-synthesized graphene devices usually require tens of hours for graphene growth, transfer, and patterning, and the flat target transfer substrate is preferred. By using this new laser scribing technology, wafer-scale graphene patterns can be obtained in ~25 minutes. Without coating photoresist for lithography, the surface of patterned graphene remains as clean as its pristine status. The results suggest that the laser scribing technology can potentially produce more economical and time-saving graphene-based circuits/systems for practical applications. It is believed that the proposed laser scribing technology could also have broad prospective applications in the graphene-based electronics, sensors and actuators systems.
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