Monolayer graphene nanoribbon p-n junction

Moghaddam, Nahid Shayesteh; Ahmadi, Mohammad Taghi; Rahmani, Meisam; Amin, N. Aziziah; Moghaddam, Hossein Shayesteh; Ismail, Razali

doi:10.1109/rsm.2011.6088336

Cited by 6 publications

(4 citation statements)

References 7 publications

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“…Using the plot, the slopes of the linear, fully transformed, regions of martensite (EM) and austenite (EA) material were calculated to be 30,000 and 40,000, respectively. The other required information, including Ms, Mf, As, Af, CM, and CA were taken from our previous studies and our readings of the literature, which were reported to be ࢤ65°C, ࢤ88°C, ࢤ23°C, ࢤ8°C, 5.7, and 8.6, respectively [ 42 , 43 , 44 , 45 , 46 ]. These material properties are summarized in Table 4 .…”

Section: Resultsmentioning

confidence: 99%

Fixation Release and the Bone Bandaid: A New Bone Fixation Device Paradigm

et al. 2017

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The current gold standard of care for mandibular segmental defeat reconstruction is the use of Ti-6Al-4V immobilization hardware and fibular double barrel graft. This method is often successful immediately at restoring mandible function, however the highly stiff fixation hardware causes stress shielding of the grafted bone and stress concentration in the fixation device over time which can lead to fixation device failure and revision surgery. The purpose of reconstructive surgery could be to create normal stress trajectories in the mandible following engraftment. We investigate the use of a two stage mechanism which separates the immobilization/healing and regenerative phases of mandibular segmental defect treatment. The device includes the use of a very stiff, Ti-6Al-4V, releasable mechanism which assures bone healing. Therefore it could be released once the reconstructed boney tissue and any of its ligamentous attachments have completely healed. Underneath the released Ti-6Al-4V plate would be a pre-loaded nitinol (NiTi) wire-frame apparatus that facilitates the normal stress-strain trajectory through the engrafted bone after the graft is healed in place and the Ti-6Al-4V fixation device has been released. Due to the use of NiTi wires forming a netting that connects vascularized bone and possibly bone chips, bone grafts are also more likely to be incorporate rather than to resorb. We first evaluated a healthy adult mandible during normal mastication to obtain the normal stress-strain distribution. Then, we developed the finite element (FE) model of the mandibular reconstruction (in the M1-3 region) with the proposed fixation device during the healing (locked state) and post-healing (released state) periods. To recreate normal stress trajectory in the reconstructed mandible, we applied the Response Surface Methodology (RMS) to optimize the Bone Bandaid geometry (i.e., wire diameters and location). The results demonstrate that the proposed mechanism immobilizes the grafted bone in the locked state properly since the maximum resultant gap (21.54 micron) between the graft and host mandible surfaces are in the safe region (less than 300 micron). By considering the von Mises criteria for failure, FE analysis together with experimental studies (i.e., compressive and tensile testing on the inferior and superior fixation devices, respectively) confirm that the proposed fixation devices do not fail, showing safety factor of at least 10.3. Based on the Response Surface Methodology (RSM) technique, the optimal parameter values for the wires are achieved (0.65 mm and 1 mm for the superior and inferior wires, respectively) and the required level of preload on each wire are calculated (369.8 N and 229 N for the inferior and superior wires, respectively). The FE results for stress distribution on the reconstructed mandible during the released state closely match that of a healthy mandible.

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Section: Resultsmentioning

confidence: 99%

Fixation Release and the Bone Bandaid: A New Bone Fixation Device Paradigm

et al. 2017

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“…[155][156][157] There has been much research interests in its photoelectron applications [158,159] and energy band structure of graphene under gate voltage. [160,161] However, electrical modulation requires additional biases and specialized processes and equipment, which limit the practical application of such graphene homogeneous pn junction.…”

Section: Electric Field Modulated Graphene Homogeneous P-n Junctionmentioning

confidence: 99%

Recent Advances in Graphene Homogeneous p–n Junction for Optoelectronics

Tian

Tang

Teng

et al. 2019

Adv Materials Technologies

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Graphene has been widely used as electrodes and active layers in optoelectronics due to its diverse excellent performances, such as high mobility, large thermal conductivity and high specific surface area etc. Methodology for constructing p-n junction has becoming an important consideration in improving the performance of optoelectronic devices and broadening of its application in related fields. Currently, graphene based p-n junction has been explored and different structures have also been investigated. This review paper summaries the recent progress on graphene homogeneous p-n junction, ranging from preparation of front-end materials (e.g. p-and n-type graphene) to building of planar and vertical p-n junctions. Furthermore, p-n junction via electrical modulation is described. The requirements for building the graphene homogeneous p-n junction, and the advantages and drawbacks of the different structures of the p-n junction are also discussed. Finally, a preferential technique to fabricate high performance p-and n-type graphene and building of the p-n junction is evaluated. This paper therefore provides an important indication on the future direction on the application of graphene in optoelectronics. 2 ranging applications, such as logical rectifier circuit [10,11] , field-effect optoelectronic transistor [12-14] , multimode non-volatile memory [15] , rectifier memory [16,17] , optoelectronic storage [18,19] , photovoltaic device [20] , photodetector [21,22] and gas sensor [23,24] etc. Consequently, it is obvious to study new material system for the p-n junction that will enhance the performance of current devices and also lead to the development of new devices. In general, p-n junction can be categorized into heterojunction and homojunction. If same materials are used, the p-n junction is known as homogeneous junction or homojunction. There are many advantages of homogeneous p-n junction, for example, there is no issue on lattice mismatch, which will result in surface defects, since p and n layers are of the same materials. Moreover, the use of the same materials in homogeneous p-n junction leads to uniform energy band gap across the device structure, as shown in Figure 1a. Depletion region is formed at the junction between p and n regions, and the alignment of Fermi level (E f) promotes band bending at the depletion region when the same semiconducting materials are used to construct the p-n junction, as represented in Figure 1b. Such homogeneous p-n junction is of great significance in the field of optoelectronics. Figure 1c illustrates the charge transport mechanism under illumination. Upon radiation of light with certain wavelength (hυ ≧ Eg), electrons jump to conduction band in p, n and depletion regions. These electrons and holes arriving at the depletion region are subsequently swept into n-type and p-type regions respectively via the built-in field. As a result, current is generated and a certain voltage is produced due to the accumulation of charges under open circuit conditions. Furthermore, this lead...

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“… 2 The purpose of mandibular reconstruction is to restore normal appearance, mastication, speech, swallowing, and breathing. 3 , 4 The most reliable means of restoring critical size or larger mandibular segmental defects is the use of a vascularized bone transfer, usually harvested from the fibula or iliac crest. 3 , 5 Typically, 1 or more surgical grade 5 (Ti–6Al–4V) 6 , 7 fixation devices are used to immobilize the graft.…”

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confidence: 99%

Metallic Fixation of Mandibular Segmental Defects: Graft Immobilization and Orofacial Functional Maintenance

Moghaddam

Jahadakbar

Amerinatanzi

et al. 2016

Plastic and Reconstructive Surgery - Global Open

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Background:The aim of this study is to investigate the behavior of the healthy mandible under maximum molar bite force to demonstrate the problems associated with the current standard of care procedures for mandibular segmental defect reconstruction (ie, use of Ti–6Al–4V hardware and either a single- or double-barrel fibular graft). With current Ti–6Al–4V mandibular reconstruction hardware, there is a significant stiffness mismatch among the hardware, graft, and the remaining host anatomy. How the distribution of mechanical forces through the mandible is altered after a segmental bone loss and reconstruction is incompletely understood.Methods:We studied a healthy adult mandible for stress, strain, and reaction force distribution during normal mastication. Stress distribution of this model was then used to study problems encountered after mandibular segmental defect reconstructive surgery. We model the use of both single- and double-barrel fibular grafts to repair the loss of the left M1–3 containing segment of the mandible. These simulations were done using 2 sets of plates with different thicknesses.Results:We found that the stiffness mismatching between the fixation hardware and the graft and host bone causes stress shielding of that bone and stress concentrations in the fixation hardware and screws. These effects are expected, especially during the bone healing period. However, long term, this abnormal stress–strain distribution may lead to either the hardware’s failure due to stress concentration or graft failure due to bone resorption as a result of stress shielding. We found that the stress–strain distribution is more normal with a double-barrel fibular graft. Additionally, we found that thinner fixation plates can reduce stress shielding.Conclusion:The proposed model can be used to evaluate the performance and optimization of the fixation device.

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Monolayer graphene nanoribbon p-n junction

Cited by 6 publications

References 7 publications

Fixation Release and the Bone Bandaid: A New Bone Fixation Device Paradigm

Fixation Release and the Bone Bandaid: A New Bone Fixation Device Paradigm

Recent Advances in Graphene Homogeneous p–n Junction for Optoelectronics

Metallic Fixation of Mandibular Segmental Defects: Graft Immobilization and Orofacial Functional Maintenance

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