Multilayer Graphene Nanoribbon Research Articles

Crosstalk noise analysis in ternary logic multilayer graphene nanoribbon interconnects using shielding techniques

SummaryThis paper presents an accurate structure for multilayer graphene nanoribbon (MLGNR) bundled interconnects to reduce the effects of crosstalk in ternary logic circuits. In the proposed structures, the signal line is surrounded by the shielding lines to reduce the crosstalk effects. The crosstalk effects such as noise peak, noise area, delay, and power consumptions are compared to effects produced by conventional methods. The impacts of process variation in the proposed structures are also presented. Additionally, the proposed MLGNR interconnect results are compared with the carbon nanotube interconnections. All the proposed circuits are implemented and simulated using HSPICE tool. The simulation results indicated that the passively shielded MLGNR interconnects provide lower crosstalk effects up to 47.7% and 69.4%, respectively, over the active and without shielded interconnects.

Temperature-Dependent Circuit Modeling and Performance Evaluation Due to Crosstalk in Capacitively Coupled Interconnects of Intercalation-Doped Multilayer Graphene Nanoribbon

The present work explores the temperature-dependent performance evaluation due to crosstalk in coupled interconnects of intercalation-doped multilayer graphene nanoribbons (ID-MLGNR). A temperature-dependent equivalent single conductor (ESC) model of arsenic pentafluoride (AsF5) ID-MLGNR is considered and is employed to analyze its crosstalk performance (i.e., crosstalk-induced noise and crosstalk-induced delay). Other metallic interconnect materials viz. mixed carbon nanotube bundles (MCB) and copper (Cu) are also analyzed in a similar manner. The temperature-dependent crosstalk performance of ID-MLGNR is compared with that of MCB and Cu, at different temperatures from 300 to 500 K. For the specified temperature range, in case of crosstalk-induced noise, the AsF5 ID-MLGNR-based long interconnects demonstrate superior performance to its MCBs and Cu counterparts. Moreover, the temperature-dependent crosstalk-induced delay is less with ID-MLGNR in comparison with both MCB and Cu interconnects. The large values of the mean free path (MFP) and conductivity of AsF5 ID-MLGNR contribute to its improved performance. In addition, the impact of variation in MFP, interlayer spacing and Fermi level is studied on the crosstalk delay performance of ID-MLGNR. From the obtained results, it is revealed that variation in these parameters results in the significant variation of 62 ps, 51 ps and 169 ps, respectively, in the odd mode (OM) crosstalk delay. Hence, for emerging nano-technology nodes (e.g., 14 nm), ID-MLGNR interconnects with its improved crosstalk performance are proposed as a potential alternative to its MCBs and Cu counterparts.

New Sensitivity Analysis on Graphene Nanoribbon Interconnects to Determine Importance of Parameters

In this paper sensitivity of a multilayer graphene nanoribbon (MGNR) interconnects parameters investigated. System sensitivity was studied on parameters like length and width in stable condition. The obtained results show with increasing width and length sensitivity will decrease and increase respectively. Impulse response diagram results show with increasing 50% width sensitivity will be zero but with increasing 50% length amplitude will decrease and the time of setting will increase. On the other hand from step response of transfer function, both width and length increase cause more stability for a system but the width parameter will be better choices for manipulating the dimension of MLGNR to reach the stable system.

Temperature dependence of the Raman spectra of multilayer graphene nanoribbons fabricated by unzipping method

The temperature dependence of Raman spectra of multilayer-graphene nanoribbons (MLGNRs) fabricated by unzipping method was investigated in the temperature range from 300 K to 700 K. MLGNRs with the width of ~200 nm are isolated and individually measured. The frequency of G band is monotonically downshifted with increasing temperature. The change in the G band frequency with temperature is reversible in thermal cycles with heating and cooling. By linear fitting, the temperature coefficient is estimated to be about −0.021 cm−1/K. This value is smaller than −0.028 cm−1/K of carbon nanotubes and larger than −0.011 and −0.016 cm−1/K of graphite and graphene, respectively, as reported previously. This means that MLGNRs are thermally stable compared with carbon nanotubes with curvatures, whereas the thermal stability of MLGNRs is lower than those of graphene and graphite. The better fitting to the G band frequency shift with temperature is obtained with nonlinear quadratic curve. From the theoretical analysis of the fitted quadratic curve, it is clarified that the downshift of G band frequency with increasing temperature is attributed to the anharmonic phonon interaction, especially 4-phonon process rather than 3-phonon process. Comparing with other nanocarbon materials reported so far, it is suggested that the strength of the anharmonic phonon interaction depends on the layer number and size of graphene.

Analysis of top- and side-contact MLGNR interconnects: impact on crosstalk, stability, and electromigration

In a recent nanoregime, the cross-coupling capacitance plays an important role due to the high packing density of integrated circuits. It can significantly affect the overall interconnect performance of an IC that can reduce the reliability, durability, and stability of silicon technology. In order to alleviate these problems, this work demonstrates shielded side-contact (SC) and top-contact (TC) multilayered graphene nanoribbon (MLGNR) interconnect to demonstrate stability and cross talk reliability issues. At 32 nm technology, an equivalent single-conductor Pi-type network is proposed for shielded SC- and TC-MLGNR for different spacing and interconnect lengths. Besides, the impact of temperature and higher current density is demonstrated. It is observed that the conventional interconnect material such as Cu exhibits 52.31% faster electromigration breakdown as compared to graphene at 1000 K. Further, the cross talk-induced delay is analyzed for shielded TC-and SC-MLGNR using driver–interconnect–load arrangement. An improved crosstalk-induced delay of 59.36% and 95.97% is observed for SC-MLGNR as compared to a TC-MLGNR with active shielding for an average spacing range of 5–20 nm at local and global lengths, respectively. Furthermore, the power delay product and peak noise of active-shielded SC-MLGNR exhibit on an average 96.82% and 38.20% improvement in comparison with active-shielded TC-MLGNR for the spacing of 5 nm at global length. Moreover, the Nyquist plot is used to demonstrate higher stability of SC-MLGNR than TC-MLGNR at 32 nm technology. Therefore, the overall system performance demonstrates that the active-shielded SC-MLGNR can be treated as a suitable choice for future VLSI technology.

Relative stability of shielded top- and side-contact MLGNR interconnects

ABSTRACT In a recent nano and deep-submicron regime, the electromagnetic interference primarily plays an important role in determining the overall interconnect performance of an integrated circuit (IC). For instance, it can cause lower reliability, and stability in silicon technology. In order to mitigate these challenges, this work introduces a new technique of active shielding by introducing a jacketed side- (SC) and top-contact (TC) multi-layered graphene nanoribbon (MLGNR) interconnect to demonstrate the relative stability. Depending on the physical configuration, an accurate Pi-type electrical network is proposed for the shielded TC-and SC-MLGNR at 32 nm technology. Using the equivalent circuit model, a fifth-order transfer function is employed to demonstrate the relative stability of SC- and TC-MLGNR at global interconnect lengths.

Investigation on the combined effects of variable Fermi energies and temperatures on the performance of multilayer graphene nanoribbon as interconnects

In the present research, the Fermi energy and temperature-dependent performance of a multilayer graphene nanoribbon (MLGNR) in terms of signal delay and power delay product (PDP) at the global interconnect length for three different technology nodes (32 nm, 22 nm, and 16 nm) were investigated in detail. A Fermi energy and temperature-dependent equivalent single conductor (ESC) based on the analytical model of MLGNR was proposed to evaluate the parasitic parameters, which capture the variations in Fermi energy and electron–phonon scattering as a function of temperature. It was found that the intercalation doping significantly raised the Fermi energy of each layer of MLGNR and consequently, increased its overall conductivity for all three technology nodes. The simulation program with integrated circuit emphasis (SPICE) tool was employed to simulate the parasitic parameters of MLGNR, and results revealed that signal delay and PDP of MLGNR increased with the increasing temperatures (200–500 K); however, gradually decreased with the rise in Fermi energy at 2000 μm length for all three technology nodes. Further, the performances of MLGNR, single-walled carbon nanotube (SWCNT), and copper interconnects were compared in the SPICE simulator, and it was noticed that the intercalation doping of MLGNR yielded a much better performance (as compared to SWCNT and copper interconnects) in terms of signal delay and PDP for all three technology nodes.

RF analysis of intercalated graphene nanoribbon-based global-level interconnects

Intercalation doping is emerging as a prospective solution to enhance the performance of graphene nanoribbon interconnects. In this paper, the radio frequency (RF) analysis of stage-2 arsenic pentafluoride- and lithium-doped multilayer graphene nanoribbons (MLGNRs) has been carried out for global-level interconnects in terms of skin depth, surface impedance, critical ratio (CR), transfer gain, and 3-dB bandwidth. The skin-depth results demonstrate that doped MLGNRs exhibit minimum performance degradation primarily due to their higher conductivity, mean free path, and momentum relaxation time as compared to neutral MLGNR. An equivalent second-order accurate RLC model of an intercalation-doped MLGNR has been used to extract the transfer gain and 3-dB bandwidth results at 14-nm technology node for global-level interconnects. The results are further evaluated by implementing an advanced π-type equivalent single conductor derived from multi-conductor transmission line model. The doped MLGNR interconnects demonstrate 11-fold enhancement of 3-dB bandwidth as compared to copper (Cu). Also, the delay and energy-delay-product (EDP) computations in time domain for doped MLGNR interconnects exhibit nearly 10 times lesser delay and significant reduction in EDP than Cu counterparts. It is also observed that optimum values for 3-dB bandwidth and EDP parameters for intercalated MLGNRs could be achieved through width optimization. The RF and transient results validate intercalated MLGNRs as a potential candidate to replace Cu for next-generation global-level interconnects.

Luminescent and Photoelectric Properties of Hybrid Structures Based on Multilayer Graphene and 0D and 2D Semiconductor Quantum Nanocrystals

Determination of regular features of mechanisms underlying interactions of nanostructured materials is one of the most important problems on the way to create the new generation of efficient photovoltaic devices. In this paper, we study the luminescent and photoelectric properties of hybrid structures that are formed on the basis of multilayer graphene nanoribbons and semiconductor quantum nanocrystals of the 0D dimension, CdSe/ZnS core/shell quantum dots, and 2D-dimension CdSe nanoplates. It is shown that the multiexponential decay of the exciton luminescence of CdSe nanoplates at room temperature is determined by the occurrence of delayed luminescence, which is caused by the presence of trap states on the surface of nanoplates. It is found that, in dry layers of nanoplates on a dielectric substrate and in the composition of hybrid structures with graphene nanoribbons, the efficiency of delayed exciton luminescence of nanoplates increases. It is shown that the rate of increase in the photoconductivity in hybrid structures based on CdSe nanoplates is an order of magnitude higher than the rate of this process in similar structures based on CdSe/ZnS quantum dots, which indicates the formation of an effective energy/charge transfer channel from nanoplates to graphene nanoribbons.

Temperature‐dependent analysis of crosstalk and delay uncertainty in multilayer graphene nanoribbon interconnects

SummaryIn this article, we have analyzed delay uncertainty due to crosstalk in multilayer graphene nanoribbon (MLGNR) interconnects. Crosstalk is a challenging problem in deep‐sub‐micron and nanometer designs. In this work, we have analyzed the crosstalk delay with a wide variation in chip operating temperature. The mean free path is modeled as a function of temperature. Furthermore, the resistance of MLGNR interconnect system is modeled. Crosstalk delay analysis is performed for both top‐contact MLGNR and side‐contact MLGNR (SC‐MLGNR) interconnects and compared the results with that of the traditional Cu interconnects. The analysis has been carried out for different interconnect widths 11, 16, and 22 nm and lengths 10, 50, and 100 μm for three different chip operating temperatures 233, 300, and 398K. The decrease in rise/fall delay (speed up) and increase in rise/fall time delay (slow down) are modeled. Finally, the delay uncertainty is modeled for different interconnect systems. The percentage change in delay values for speed up and slow down cases are −23.4%, −29.8% and 114.4%, 161.9%, respectively, for 10μm SC‐MLGNR interconnect. It is shown that the delay uncertainty is significantly less in SC‐MLGNR interconnects and with the advancement of technology the performance is improved as compared with copper interconnects.

The analytical model of frequency response and bandwidth for coupled multilayer graphene nanoribbon interconnects

This paper applies the multilayer graphene nanoribbons (MLGNR) as a prospective candidate material to replace the conventional copper (Cu) for next generation on-chip interconnects. Based on the equivalent single conductor (ESC) modeling, a distributed transmission line model for coupled MLGNR interconnects is presented to obtain the transfer gain and 3-dB bandwidth at the global level of 14 ​nm technology node, which take the in-phase and out-of-phase crosstalk modes into consideration, and verified with the Hspice simulation. It is demonstrated that the MLGNR and Cu interconnects under in-phase mode have a larger transfer gain and a wider 3-dB bandwidth than that under out-of-phase mode, and MLGNR interconnects can more effectively improve the transfer gain and 3-dB bandwidth compared with Cu interconnects at the same conditions. The numerical calculation results show that, decreasing interconnect temperature, increasing line space and increasing driver and load sizes are efficient ways to enhance the transfer gain and 3-dB bandwidth for MLGNR and Cu interconnects. Moreover, the top contact MLGNR (TC-MLGNR) also can be used as an emerging material for on-chip interconnects to replace the conventional Cu. In addition, it is found that the results obtained by the proposed model are in good matching with Hspice simulation and the maximum relative deviation for them is less than 4%, meanwhile the efficiency of CPU runtime is improved over 90% by using the proposed model, as compared to Hspice simulation. The results presented in this paper would be useful to design the on-chip interconnects with better bandwidth characteristics.

Novel Approach to Analyze Crosstalk for a Multi-Line Bus System at 32-nm Technology

This research paper presents a novel approach to analyze the crosstalk-induced delay of multi-layered graphene nanoribbon (MLGNR) and multi-walled carbon nanotube (MWCNT) interconnects. A multi-line driver-interconnect-load (DIL) system is employed to analyze the crosstalk-induced delay for different switching transitions. The interconnect lines of the proposed DIL are said to be operated by either a resistive or a CMOS, or a CNFET driver for different switching transitions at 32-nm technology. Using the unique CNFET driver, the victim line of the multi-level MLGNR/MWCNT-based bus system experiences a delay almost 57.25% and 31.62% lesser in comparison to a resistive driver and a CMOS interconnect driver, respectively. Additionally, the overall worst-case delays are reduced by 89.45% and 98.98% for MLGNR in comparison to an equivalent MWCNT at 100[Formula: see text][Formula: see text]m and 1,000[Formula: see text][Formula: see text]m interconnect lengths, respectively.

Impact of Intercalation Doping on the Conductivity of Multi-Layer Graphene Nanoribbon (MLGNR) in On-Chip Interconnects

Graphene nanoribbons are considered potentially suitable and have exhibited excellent results in on-chip interconnects. In order to evaluate the different circuit impedance parameters of multi-layer graphene nanoribbons (MLGNRs), an electrical equivalent single conductor (ESC) along with an analytical model is proposed. On the basis of an electrical model, the impact of intercalation doping on the performance of MLGNRs at 32, 22, and 16[Formula: see text]nm technology nodes is discussed in this paper. Moreover, it is also discussed that the increase in intercalation doping increases the Fermi energy of the layers of the MLGNR, which increases its overall conductivity. The fact that the variation in the Fermi energy will have a considerable impact on the parasitic parameters of the MLGNR interconnect at three different technology nodes (32, 22, and 16[Formula: see text]nm) for variable global lengths (500–2000[Formula: see text][Formula: see text]m) is also analyzed. To estimate and compare the performance in terms of delay and power delay product (PDP) of MLGNRs, the simulation program with integrated circuit emphasis (SPICE) simulation tool is used. The results also show that the increase in the Fermi energy improves the performance of MLGNRs in terms of delay and PDP at three different technology nodes. Furthermore, a comparative analysis of all three technology nodes is performed with the copper interconnect, and it is revealed that the MLGNR interconnect is considered to be a prominent material for the next-generation on-chip very-large-scale integration interconnects.

Performance and signal integrity analysis of intercalation‐doped MLVGNR interconnects

In this work, signal integrity, power consumption and stability of multilayer vertical graphene nanoribbon (MLVGNR) interconnects are determined and compared with multilayer horizontal GNR (MLHGNR) and conventional copper interconnects for different intercalation dopants and specularity indices. Lithium-intercalated MLVGNR outperforms these conventional interconnects in terms of delay. However, it is not very much immune to noise and also consumes more power but overall noise delay product and power delay product are least among all. As far as stability is concerned, MLVGNR interconnects have a comparable gain and phase margin and a steep transient response without an undershoot as compared with other interconnect configurations, which experience undershoot. It is worth to point out that MLVGNR interconnects are more amenable to scaling compared with other alternatives. This study for the first time analyses and compares the performance, signal integrity and stability of MLVGNR, MLHGNR and copper interconnects.

Temperature-dependent crosstalk between adjacent MLGNR interconnects of different dimensions and its impact on gate oxide reliability

A comprehensive analysis is carried out herein on the impact of the interconnect geometry with nanoscale dimensions on the crosstalk-induced gate oxide reliability in coupled multilayer graphene nanoribbon (MLGNR) interconnects. Simplified circuit models are used to capture the temperature-dependent phonon scattering at temperatures from 300 to 500 K. Three different cases (case-1, case-2, and case-3) of coupled interconnects with fixed sum of width and spacing (interconnect pitch) but varying width/spacing (w/s) ratio are analyzed, revealing that the coupled interconnect geometry controls the impedance parameters. Functional crosstalk analysis shows that the highest positive noise peak of the victim output over the temperature range from 300 to 500 K is obtained in case-3, where the w/s ratio is maximum. On the other hand, the reverse is true for the time duration of the noise pulse at the far end of the victim line in case-2. Analysis of the dynamic crosstalk then reveals that an average percentage delay of approximately 13.45% is obtained in case-3 with respect to (w.r.t.) case-1, while a marginal difference is found in case-2. In comparison with temperature-independent circuit models, the results obtained using the temperature-dependent circuit models of the coupled MLGNR interconnects show an average relative improvement in the time duration of the noise pulse at the victim output by approximately 39%, 35.6%, and 46.6% in case-1, case-2 and case-3, respectively, for the different lengths. The gate oxide reliability in terms of the average failure rate (AFR) for coupled MLGNR interconnects with different widths and lengths is further investigated. The results show an infinitesimal increment of the AFR with the increase in the width and length of the MLGNR interconnects. Moreover, they reveal that the interconnect geometry in case-3 is more prone to gate oxide failure compared with the other cases.

Collaborative Applying the Ultra-low-k Dielectric and the High-k Dielectric Materials for Performance Enhancement in Coupled Multilayer Graphene Nanoribbon Interconnects

Based on transmission line modeling, a new technology of collaborative applying the ultralow-k dielectric and the high-k dielectric materials in coupled multilayer graphene nanoribbon (MLGNR) interconnects (i.e., case 4) to reduce propagation delay and to expand 3-dB bandwidth of the conventional pristine (undoped) MLGNR interconnects is proposed in this paper. By using the decoupling technique and ABCD parameter matrix approach, the transfer function of the equivalent circuit model for coupled MLGNR interconnects is derived to obtain step response, propagation delay, transfer gain and 3-dB bandwidth under in-phase and out-of-phase crosstalk modes at global level of 7.5 nm technology node, which is based on the defined four cases. The results show that the maximum reduction of propagation delay between the proposed new technology (case 4) and the conventional MLGNR interconnects (case 1) can reach 15.911 ns at out-of-phase crosstalk mode for an interconnect length of 4000 μm. The corresponding 3-dB bandwidth for them can be expanded over 2.978 times in the same length as the former. It is demonstrated that the proposed case 4 can obviously reduce the propagation delay and enhance the transfer gain and 3-dB bandwidth compared with the conventional case 1. Moreover, it is found that the coupled MLGNR interconnect under in-phase mode outperform that under out-of-phase mode in terms of propagation delay, transfer gain and 3-dB bandwidth at the same condition. In addition, it is manifested that the victim line of two-line coupled MLGNR interconnects have lesser propagation delay, higher transfer gain and larger 3-dB bandwidth, as compared to three-line coupled MLGNR interconnects at the same case. The proposed new technology in this paper would be beneficial to improve the performance of MLGNR interconnects and to provide the guidelines for the design of next generation on-chip MLGNR interconnect system.

Thermal model for 3-D integrated circuits with integrated MLGNR-based through silicon via

This paper applies the multi-layer graphene nanoribbon as a new prospective filler material for through silicon via to solve the complex heat problems in the 3-D integrated circuits. An equivalent thermal model for 3-D integrated circuits with the MLGNR-based through silicon via is presented in this work, which take lateral heat transfer of through silicon via into account. The experimental results show that the heat transfer performance of MLGNR-based through silicon via is better than the conventional Cu-based through silicon via. Furthermore, it is found that the temperature predicted by the proposed model are in good accordance with the ANSYS simulation, and the maximum relative deviation is less than 4.0%

The insertion of high-k dielectric materials in multilayer graphene nanoribbon interconnects for reducing propagation delay and expanding bandwidth

Abstract The multilayer graphene nanoribbons (MLGNR) by inserting the high-k dielectric material between adjacent graphene nanoribbons (GNR) layers to reduce propagation delay and to expand bandwidth of the conventional pristine (undoped) MLGNR interconnects is presented in this paper. An equivalent distributed circuit model of the proposed MLGNR interconnect with high-k dielectric materials is established to derive the analytical expressions of propagation delay, step response, transfer gain and 3-dB bandwidth for 7.5 nm technology node at global level. The numerical simulation results show that the maximum reduction of propagation delay between the proposed MLGNR by inserting SrTiO3 dielectric material and the pristine MLGNR can reach 12.746 ns for an interconnect length of 4000 μm. The corresponding 3-dB bandwidth for them can be expanded over 4 times for the interconnect length. It is demonstrated that the proposed MLGNR by inserting the high-k dielectric material can greatly reduce propagation delay and enhance transfer gain and 3-dB bandwidth compared with the conventional pristine MLGNR interconnects. Moreover, it is found that the results obtained by the proposed model have close agreement with Synopsys HSPICE simulation and the maximum relative error for them is less than 5%, and the average efficiency of CPU runtime is improved 95% by using the proposed model, as compared to HSPICE simulation. The proposed design method has many potential applications in improving performance of MLGNR interconnect and providing guidelines for the next generation on-chip interconnect system.

Impacts of Process and Temperature Variations on the Crosstalk Effects in Sub-10 nm Multilayer Graphene Nanoribbon Interconnects

In this study, a comprehensive analysis of the crosstalk in multilayer graphene nanoribbon (MLGNR) interconnects in the presence of process and temperature variations is performed. The variations of the crosstalk delay, crosstalk noise area, and power are investigated in the presence of process and temperature variations for passively shielded five-line MLGNRs carrying ternary signals in 10nm and 7nm technology nodes. Analyses are conducted considering all of the important sources of process variations using comprehensive Monte Carlo simulations. The results indicate that the impacts of the process and temperature variations on the crosstalk effects become more evident with the technology scaling from 10 to 7nm, mainly due to the reduction of the width and spacing of the interconnects. According to the results, the maximum deviation of the crosstalk delay, power consumption, and noise area are 160ps, $0.9{\mu }\text{W}$ and 16V.ps, respectively for 10nm passively shielded MLGNR interconnect in the presence of all sources of process variations. These values are in turn 335ps, $1.3{\mu }\text{W}$ , and 27V.ps in 7nm node. Moreover, the crosstalk effects are evaluated at various temperatures ranging from 200°K to 450°K. The maximum variations for the crosstalk delay and noise area for 10nm MLGNR interconnects are 57ps and 6V.ps at temperatures higher than room temperature and 6ps and 0.5V.ps for temperatures lower than the room temperature. These variations are in turn 118ps, 9V.ps, 12ps and 1V.ps for 7nm MLGNR interconnects. It is also observed that the variations of the resistance of the $500{\mu }\text{m}$ length MLGNR in the presence of temperature variations are on average 3.9 $\text{K}\Omega $ and 8.2 $\text{K}\Omega $ in 10nm and 7nm technologies, respectively.

Graphene/fluorographene heterostructure for nano ribbon transistor channel

4H-SiC multilayer graphene/fluorographene heterostructures have been implemented to fabricate a 40 nm transistor channel. The plasma-assisted fluorination process with a carbon-to-fluorine ratio of ∼1 allows the passivation of the sidewalls with a substantial reduction in the channel width to form multilayer graphene nanoribbons (GNRs). A graphene channel is completely embedded in the passivated top and sidewalls of graphene. the gate leakage is in the nanoampere range, which makes the fluorinated dielectric robust enough for tunnel barrier. We have fabricated top gate transistors using this heterostructure and demonstrated the onset of rectification using this process. Despite the limited on/off ratio, I–V characteristics of GNRs of 40 nm channel width show a clear improvement compared to 50 μm device indicating that this process is a potential route to pattern nanoribbons.