Low-pressure Chemical Vapor Deposition Method Research Articles

Low-Temperature Synthesis of Linear Carbon Chain inside Single-Walled Carbon Nanotubes

Linear carbon chain (LCC) has attracted much interest concerning its structure and applications. It has been reported that LCC possesses higher strength, elastic modulus, and stiffness than any known material, which provides a possibility for LCC as a new composite material, yet its chemical stability remains an issue [1]. Therefore, finding a method to efficiently synthesize LCC has become a meaningful research topic in recent years. A landmark study on LCC synthesis was given by using double-walled carbon nanotubes (DWCNTs) as the template combined with a high-temperature annealing treatment at 1460°C to acquire long chains composed of more than 6,000 carbon atoms [2]. Except for DWCNTs, LCC synthesis starting from single-walled carbon nanotubes (SWCNT) as templates was also reported. However, given the instability of SWCNTs at higher temperature [2] the synthesis efficiency is not as good as for DWCNTs. As far as we know, there is still no report on an efficient LCC synthesis inside SWCNTs. Herein, we report the low-temperature (400°C) efficient LCC synthesis starting from a SWCNT template.To this end, a SWCNT dispersion [3] underwent a surfactant exchange process and was fabricated into a SWCNT film by the filtration method. The SWCNT film was annealed under 400°C in an argon atmosphere to synthesize LCC. Raman spectroscopy (laser wavelength 532 nm) was used to characterize the efficiency of the LCC synthesis. A strong peak at 1863 cm-1 appeared after annealing, originating from the well-known C-mode of the linear carbon chain [4] thereby confirming its existence inside SWCNTs. SWCNTs synthesized by a low-pressure alcohol catalytic chemical vapor deposition (ACCVD) method [5] were also adopted for the LCC synthesis template, resulting in a similar LCC Raman peak at 1863 cm-1. We attribute this successful low-temperature LCC synthesis to the appropriate surfactant which could be encapsulated inside CNTs and converted to LCC during the annealing process.Keywords: Linear Carbon Chain, Single-walled Carbon Nanotubes, Surfactants

Unveiling structural and optical properties of Sn-doped β-Ga2O3: A correlation of experimental and theoretical observations

This work presents the experimental and theoretical insights into the structural and optical properties of tin (Sn)-doped β-Ga2O3. Sn-doped β-Ga2O3 films were fabricated using the low-pressure chemical vapor deposition (LPCVD) method onto the c-plane sapphire substrate. Further, deposited thin films were characterized for their structural and optical properties. XRD pattern depicts the crystalline nature of β-Ga2O3. The energy band gap (Eg) obtained from UV–Vis spectra has been decreased from 4.82 eV to 4.77 eV for as-deposited β-Ga2O3 to Sn-doped β-Ga2O3, respectively. However, an increase in absorbance has been observed in Sn-doped β-Ga2O3 films. Further, the first principle study based on density functional theory (DFT) has been used to comprehend the effect of Sn doping in β-Ga2O3 films. DFT result reveals the expansion of the lattice parameter of intrinsic β-Ga2O3 on the introduction of the Sn atom. Furthermore, a reduction in Eg has been observed upon Sn doping into the β-Ga2O3 structure similar to the experimental results. The reason behind the reduction in the Eg may be due to the Sn-5s energy level at the bottom of the conduction band as revealed in density of state (DOS) investigations. Also, the DOS results of Sn-doped β-Ga2O3 suggest that the atom has tended to form the ionic bond characteristics with the introduction of Sn into the β-Ga2O3, where the free electrons of the Sn-5s orbital state will fill the conduction band and may improve the conductivity. Additionally, optical properties such as reflectance and dielectric loss of function have been investigated. The reflectance and dielectric loss of function result proposed that more energy was absorbed when Sn was introduced to β-Ga2O3. Therefore, our observation suggests that upon Sn doping into β-Ga2O3, optical as well as structural properties were improved and these improved properties may be useful for optoelectronic devices.Novelty statementβ-Ga2O3 is an emerging material for optoelectronic device applications due to its excellent wide energy band gap, high critical electric field strength, high melting point, high Baliga figure of merits (BFOM), and exceptional physical and chemical stability. However, intrinsic β-Ga2O3 suffers from poor mobility and surface defects. Therefore, β-Ga2O3 needs a dopant material to enhance its' structural and optical properties. In this case, Sn doping may improve the optoelectronic properties of β-Ga2O3. Therefore, detailed theoretical and experimental investigations on Sn-doped β-Ga2O3 become necessary to understand inside phenomena. However, lots of experimental and theoretical works have been performed on Sn-doped β-Ga2O3. But, to date, there is no available report related to the correlation of theoretical and experimental data-based studies on Sn-doped β-Ga2O3. In this work, we have explored the structural and optical properties of Sn-doped β-Ga2O3 thin films deposited by the LPCVD method on the c-plane sapphire substrate. Further, the experimental results obtained were correlated with the first principal based DFT results. Our observation suggests that upon Sn doping into β-Ga2O3, optical as well as structural properties were improved and these improved properties may be useful for optoelectronic devices.

Performance and stability improvement of CVD monolayer MoS2 transistors through HfO2 dielectrics engineering

Monolayer molybdenum disulfide (MoS2) is a promising semiconductor channel material for future electronics due to its atomic thickness and high mobility. However, conventional back-gate MoS2 transistors suffer from substantial scattering caused by substrate and surface adsorbates, which impair carrier mobility and device reliability. In this work, we demonstrate an exemplary dielectric engineering approach that uses atomic-layer-deposited hafnium oxide (HfO2) as the gate dielectric and channel passivation layer to improve device performance and positive bias instability. The large-single-crystal monolayer MoS2 film was directly synthesized on SiO2/Si substrates by a low-pressure chemical vapor deposition method. MoS2 transistors with various dielectrics were fabricated and characterized for a fair comparison. The mobility increased from 4.2 to 19.9 cm2/V·s by suppressing charged impurities and phonon scattering when transferring the MoS2 channel from 100 nm SiO2 substrates to 20 nm HfO2 substrates. Passivation of another 10 nm HfO2 on the back-gate transistors further increased the mobility to 36.4 cm2/V·s with a high drive current of 107 μA/μm. Moreover, the threshold voltage shift of the passivated transistor was reduced by about 58% from 1.9 to 0.8 V under positive bias stress. This is due to the fact that channel passivation with HfO2 effectively eliminated charge trapping of adsorbed substances. These results reveal that HfO2 gate dielectric and passivation by atomic-layer deposition are effective methods to improve the performance and stability of MoS2 devices.

Low-Pressure CVD Synthesis of Tetragonal Borophene Single-Crystalline Sheets with High Ambient Stability

Being a typical graphene-like two-dimensional (2D) material, borophene has received a lot of attention due to its low density, high electron mobility, large Young’s modulus, and good chemical stability. Compared with the corresponding bulk counterparts, 2D borophene has larger specific surface area, higher conductivity, and smaller work function, finding potential applications in high-speed transistors, optoelectronic detection, field emission (FE), and mechanical enforcement areas. In this paper, 2D tetragonal borophene sheets with high ambient stability have been successfully fabricated on the surface of 1 cm2 copper foil using a developed low-pressure chemical vapor deposition (LPCVD) method. The vapor–solid mechanism was used to comprehend the formation of the tetragonal borophene sheets. The electrical conductivity of individual borophene sheets ranged from 4 to 5 × 10–4 S/cm, and the band gap was about 2.1 eV, suggesting their narrow semiconductive nature. Also, the maximum FE current of individual borophene sheets was close to 1 μA, and their emission properties enhanced with the decreasing sheet thickness, comparable to many other nanomaterials with excellent FE performances. More interestingly, individual borophene sheets were found to retain good enough electrical transport and FE behaviors even if they experienced several days’ atmospheric conservations. Our research results suggest that the LPCVD-grown borophene may be a promising building block for constructing high-performance nanodevices with good ambient stability.

Boron Carbonitride Films with Tunable Composition: LPCVD and PECVD Synthesis Using Trimethylamine Borane and Nitrogen Mixture and Characterization

This study reports the chemical vapor deposition of amorphous boron carbonitride films on Si(100) and SiO2 substrates using a trimethylamine borane and nitrogen mixture. BCxNy films with different compositions were produced via variations in substrate temperature and type of gas-phase activation. The low-pressure chemical vapor deposition (LPCVD) and plasma-enhanced chemical vapor deposition (PECVD) methods were used. The “elemental composition—chemical bonding state—properties” relationship of synthesized BCxNy was systematically studied. The hydrophilicity, mechanical, and optical properties of the films are discussed in detail. The composition of films deposited by the LPCVD method at temperatures ranging from 673 to 973 K was close to that of boron carbide with a low nitrogen content (BCxNy). The refractive index of these films changed in the range from 2.43 to 2.56 and increased with temperature. The transparency of these films achieved 85%. LPCVD films were hydrophilic and the water contact angles varied between 53 and 63°; the surface free energy was 42–48 mN/m. The microhardness, Young’s modulus and elastic recovery of LPCVD films ranged within 24–28 GPa, 220–247 GPa, and 70–74%, respectively. The structure of the PECVD films was close to that of hexagonal boron nitride, and their composition can be described by the BCxNyOz:H formula. In case of the PECVD process, the smooth films were only produced at low deposition temperatures (373–523 K). The refractive index of these films ranged from 1.51 to 1.67. The transparency of these films achieved 95%; the optical band gap was evaluated as 4.92–5.28 eV. Unlike LPCVD films, they were very soft, and their microhardness, Young’s modulus and elastic recovery were 0.8–1.4 GPa, 25–26 GPa, and 19–28%, respectively. A set of optimized process parameters to fabricate LPCVD BCxNy films with improved mechanical and PECVD films with high transparency is suggested.

Preliminary bond capacity exploration between monolayer graphene and cementitious composites

This study aims to explore bond capacity between monolayer graphene and cementitious composites for the first time through a pullout test. The low-pressure chemical vapor deposition method was used to synthesize monolayer graphene on the copper substrate to be embedded in the mortar made by the briquette mold. The bond capacity between them was higher than the tensile strength of the copper sheet with as-grown monolayer graphene on the surface since all specimens failed in fracture with embedment length of more than 30 mm. The monolayer graphene enhanced the copper tensile fracture stress and normalized energy during the test as the copper sheet width increased. This short communication explores a new path to quantify the bond between the monolayer graphene and the mortar to promote the understanding of the behavior of graphene-enhanced cementitious composites.

Study on factors impacting the fabrication of large-sized graphene single crystals in the quasi-sealed restricted growth chamber

In this study, a quasi-sealed restricted growth chamber was designed to fabricate large-sized graphene single crystals by the low-pressure chemical vapor deposition (LPCVD) method. The results indicated that large-sized graphene single crystals were easier to be fabricated in the restricted growth chamber, which was about 6.8 times larger than that fabricated in the traditional growth chamber, indicating a higher growth rate of the graphene in the former. And the graphene nucleation density in the restricted growth chamber is lower than that in the traditional one. Meanwhile, graphene's nucleation density was further suppressed by using the oxide layer passivated copper substrates in the restricted growth chamber. With the help of the finite element numerical simulations and Newtonian fluid theory, the impacting mechanism of those two growth chambers on graphene nucleation and growth was also investigated. The results showed that the restricted chamber constructed a near-static growth environment for graphene, which not only significantly reduced the mass transfer rate of the carbon source above the substrate, but also helped prolong the residence time owing to the viscous force and the friction force.

Synthesis of Large-Area Single- to Few-Layered MoS2 on an Ionic Liquid Surface.

Large-area fabrication of transition metal dichalcogenides via environmentally friendly and efficient processes has been a long-standing issue in the field of two-dimensional (2D) materials. Here, we report that single- to few-layered MoS2 sheets with an average size of the order of micrometers have been successfully synthesized on an ionic liquid surface by a modified low-pressure chemical vapor deposition (LP-CVD) method without the assistance of catalysts. It is found that the MoS2 sheets grown on the liquid substrate exhibit a complete molecular crystal structure, which is confirmed by transmission electron microscopy (TEM), Raman spectroscopy, and photoluminescence (PL) spectroscopy measurements. The interlayer spacing does not change significantly with the increase of the MoS2 layers, corresponding to a layer-by-layer growth pattern. The growth mechanism of the MoS2 sheets is presented according to the experimental results. The work provides a new and simple method of preparing more molecular crystals on liquid substrates and will contribute to further research in this field.

Engineering SERS Properties of Silicon Nanotrees at the Nanoscale

Large specific surface area nanostructures are desirable in a wide range of sensing applications due to their longer light-trapping path and increased absorption. Engineering of the specific nanotree structure which possesses a high branch density turned out to be challenging from the experimental point of view, and certainly not adequately explored. This paper shows how to design substrates with a silicon nanotree structure for surface-enhanced Raman spectroscopy (SERS) applications. Silicon nanotrees were synthesized by a Ag-Au nanocluster-catalyzed low-pressure chemical vapor deposition method (LPCVD). By the presented approaches, it is possible to manipulate branches’ number, length and thickness. The synthesized nanostructures are flexible after immersion in water which improves SERS performance. The amount of sputtered metal played a key role in preserving the flexibility of the nanotree structure. The obtained substrates with highly fractal nanostructure were tested on 4-mercaptophenylboronic acid (MPBA) to match the optimal SERS parameters. The silicon nanotrees fabrication, and particularly obtained SERS substrates plated with Ag and Au nanoparticles, demonstrated good features and a promising approach for further sensor development.

Towards n-type conductivity in hexagonal boron nitride

Asymmetric transport characteristic in n- and p-type conductivity has long been a fundamental difficulty in wide bandgap semiconductors. Hexagonal boron nitride (h-BN) can achieve p-type conduction, however, the n-type conductivity still remains unavailable. Here, we demonstrate a concept of orbital split induced level engineering through sacrificial impurity coupling and the realization of efficient n-type transport in 2D h-BN monolayer. We find that the O 2pz orbital has both symmetry and energy matching to the Ge 4pz orbital, which promises a strong coupling. The introduction of side-by-side O to Ge donor can effectively push up the donor level by the formation of another sacrificial deep level. We discover that a Ge-O2 trimer brings the extremely shallow donor level and very low ionization energy. By low-pressure chemical vapor deposition method, we obtain the in-situ Ge-O doping in h-BN monolayer and successfully achieve both through-plane (~100 nA) and in-plane (~20 nA) n-type conduction. We fabricate a vertically-stacked n-hBN/p-GaN heterojunction and show distinct rectification characteristics. The sacrificial impurity coupling method provides a highly viable route to overcome the n-type limitation of h-BN and paves the way for the future 2D optoelectronic devices.

Fabrication of n+-poly-Si/p+-c-Si tunnel diode using Low-pressure Chemical Vapor Deposition for Photovoltaic Applications

In this paper, an n+-poly-silicon/p+-crystalline-silicon tunnel diode has been fabricated and characterized. The n+ poly-silicon layer is deposited by the low-pressure chemical vapor deposition method, while a diffusion furnace is used for boron diffusion in crystalline silicon. Scanning electron microscopy and X-ray diffraction pattern have been used for structural characterization. Hall measurement and current-voltage characteristics have been used for carrier density, mobility, current density, and contact resistance measurement. Hall measurement reveals the carrier density of ~1019 cm-3 in phosphorus-doped poly-silicon tunnel layer with mobility of ~5.4 cm2 V-1-s-1. The current-voltage characteristics of the tunnel diode show the current density of ~103 Ampere/cm2 at a voltage of 0.1 Volt. Using tunnel diode, an n+-poly-Si/p+-c-Si/n-c-Si/n+-c-Si structure has been fabricated for photovoltaic application. This structure generates a current density of ~17.9 mA/cm2 and a voltage of 601 mV for a 195±10 nm thick doped poly-silicon layer. Further, to improve the solar cell’s performance, a thin layer of poly-silicon has been used.

The effects of post-annealing technology on crystalline quality and properties of hexagonal boron nitride films deposited on sapphire substrates

Highly c-axis oriented hBN films were deposited onto sapphire substrates by a low-pressure chemical vapor deposition method. The influences of the post-annealing technology, including annealing temperatures (1500–1700 °C), annealing time (5–30 min), and annealing ambient (N2, H2, and Ar), on the crystalline quality and optical and photoelectric properties of deposited hBN films have been investigated. The post-annealing treatment can not only improve the ordering of hBN domains and remove the defects in hBN films, but also promote the growth of hBN grains and decrease the grain boundaries. The optimal crystalline quality was obtained when hBN films were annealed in N2 ambient at 1700 °C for 10 min. As for the hBN films annealed at the optimum conditions, average longitudinal and transverse sizes of hBN grains are estimated to be respectively about 27 and 108 nm, and the intrinsic absorption edge and the optical bandgap are severally 215 nm and 5.79 eV. Moreover, the photoelectric responsibility of an ultraviolet photodetector based on the annealed hBN films, whose cutoff wavelength is less than 224 nm, was increased by 8 times.

Piezo-resistive effects of Area-arrayed Dumbbell-Shape Graphene Nano-ribbon Structure for Highly Sensitive Micro-Scale Tactile Sensor

In order to develop a highly-sensitive small-scale tactile sensor, piezoresistive effect of graphene nanoribbon was applied to the sensor. It was confirmed that the graphene nanoribbon narrower than about 70 nm showed semiconductive properties and thus, large piezo-resistive constant. The dumbbell shape was applied to the stable junction between metallic graphene and semiconductive graphene. It was easy to form stable ohmic contact between the metallic graphene and metallic electrode. An area-arrayed nanoscale GNR structure with varying width was fabricated for a highly sensitive tactile sensor. Graphene was synthesized inside a copper pocket using a low-pressure chemical vapour deposition (LP-CVD) method. PMMA- assisted wet transfer process was used to transfer graphene grown on the copper to the target substrate. Then, the electrodes were deposited using electron-beam deposition. A four-point bending test was carried out on the sensor to determine the piezo-resistive effect of the DS-GNR. Finally, the gauge factor was determined under the application of various amounts of strain.

Effect of staged methane flow on morphology and growth rate of graphene monolayer domains by low-pressure chemical vapor deposition

Although many efforts have been spent on graphene growth, there is still a lack of comprehensive understanding about the growth mechanism and precise control for different morphologies of graphene domains synthesis though carbon precursor. In this work, controlled single-crystal graphene monolayer domains with different morphologies of four, six and multiple symmetry have been achieved just by staged modulation of methane flow through low-pressure chemical vapor deposition method on copper. The growth rate can also be regulated by the methane flow, and the highest growth rate can reach 25 μm/min corresponding to the multiple-dendritic shape. The schematic structure of the different shapes with active sites has been proposed to understand the formation mechanism of different graphene domains. Synthesis single crystal graphene with various morphologies will be of great promising potential applications in catalytic and many other fields.

Synthesis of Cs2SnI6 perovskite thin film by low-pressure chemical vapor deposition method

Cs2SnI6 is an all-inorganic, air-stable and Pb-free halide perovskite material. In this work, we propose a low-pressure chemical vapor deposition method that enables the synthesis of continuous Cs2SnI6 thin films. Some technical parameters such as the deposition time and the deposition temperature of CsI were varied to investigate the morphology and thickness of Cs2SnI6 thin films. The film was further undergone an annealing treatment in SnI4 ambient to enhance characteristics, such as the long-term stability and the structural, optical and electrical properties. After annealing in SnI4, the film was found to be stable in ambient air (40–60% humidity) for 30 days. The film shows n-type semiconducting with an energy bandgap of 1.58 eV. Its absorption coefficient is higher than 3.4 × 104 cm−1 in the visible region with a maximum value of 0.9 × 105 cm−1 at the wavelength of 420 nm. The carrier concentration increased to 5.5 × 1017 cm−3, and the resistivity declined to 3.1 Ω.cm.

Mechanistic investigation of aluminide coating formation by low-pressure chemical vapor deposition method on NiCoCrAlY coating in presence of nickel-ceria composite layer

In this study, a hybrid coating comprised of NiCoCrAlY fabricated by HVOF method, Ni–CeO2 composite coated by electrodeposition, and aluminide coating applied by low pressure chemical vapor deposition (LPCVD) method are investigated. To elucidate the formation process of aluminide coating, the microstructure and properties of the applied coatings were examined by field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), and EDS analyses. It was concluded that the desired β-NiAl phases are uniformly created within a single step on the surface. Furthermore, with the extending of the coating duration from 2 to 4 h, the thickness of the aluminide coating was increased from 14 to 25 μm. The thickness values were increased even further in the presence of Ni–CeO2 coating, where the growth mechanism was also changed. Within 4 h, a coating with a thickness of roughly 50 μm was obtained. Moreover, in the presence of Ni–CeO2 coating, it was observed that the inward diffusion of aluminum was predominant at the beginning of the process, whereas with longer processing durations, the outward diffusion of the nickel becomes dominant instead.

Temperature dependent Raman scattering of directly grown twisted bilayer graphene film using LPCVD method

To get insight into the thermal management of twisted bilayer graphene based devices, the interpretation of temperature variation on twisting properties becomes crucial. In this aspect, we report the temperature dependent Raman scattering of twisted bilayer graphene (tBLG) on the Si substrate having SiO2 thickness 300 nm. The tBLG samples have been directly grown on the copper foil substrate using a home-built low pressure chemical vapor deposition (LPCVD) setup. The temperature dependent Raman scattering has been studied on two samples of tBLG named as tB1 and tB2. The twisting nature of bilayer graphene film has been analyzed using R, G, and 2D peak characteristics in Raman spectra. The Raman mapping with respect to different peak parameters of G and 2D peak (intensity, width, and position), intensity ratio (I2D/IG) has been employed to probe the uniformity of tBLG film. In tB1, the R peak has been found at 1395.82 cm−1 and not observed in sample tB2 at room temperature. The temperature dependence of G and 2D peak frequency in Raman spectra has been investigated in the temperature range from 80 to 450 K. In tB1 and tB2, the temperature coefficient of G peak has been found to be - (0.97 ± 0.34) × 10−2 cm−1/K, and - (1.08 ± 0.15) × 10−2 cm−1/K, respectively. Further, the extracted value of temperature coefficient of 2D peak in tB1, and tB2 are - (2.92 ± 0.80) × 10−2 cm−1/K, and - (3.01 ± 0.29) × 10−2 cm−1/K respectively. Additionally, the twist angle has been estimated as ∼23°-27° for T ≤ 300 K and 3°-8° for T > 300 K in tB1. In tB2, it has been found to be ∼13°-16° for the temperature range of 80–200 K and 5°-9° for 250–450 K. These findings shed light on the twisting behavior of bilayer graphene film and its anharmonic properties.

Growth of hexagonal boron nitride films on silicon substrates by low-pressure chemical vapor deposition

By respectively using Boron trichloride and ammonia as the boron source and the nitrogen source, and nitrogen as the carrier gas, hexagonal boron nitride films were grown on (100) silicon substrates via a low-pressure chemical vapor deposition method in a deposition temperature range of 900–1300 °C with a total pressure of 100 Pa. The effect of temperature on crystalline quality of the hexagonal boron nitride films was investigated using X-ray diffraction and Raman spectra. It was demonstrated that stoichiometric polycrystalline hexagonal boron nitride films were synthesized at 1200 °C. A deep-ultraviolet photodetector based on a 2.3 µm hBN film exhibited a photo-to-dark-current ratio of ~ 312 at 20 V bias under the irradiation of a UV-enhanced xenon lamp. It indicates that hBN films are promising functional materials for high-performance solar-blind photodetectors.

Controlled Deposition of Lead Iodide and Lead Chloride Thin Films by Low-Pressure Chemical Vapor Deposition

Lead halide thin films, such as lead iodide (PbI2) and lead chloride (PbCl2), are used as precursor films for perovskite preparation, which is frequently achieved by vacuum thermal evaporation but rarely by the low-pressure chemical vapor deposition (CVD) method. Here, we report on the deposition of PbI2 and PbCl2 thin films on glass substrates by employing the low-pressure CVD method. The effect of the substrate temperature on the structure and morphology of the lead halide films is investigated. Crystalline films were realized for both lead halides, with PbI2 films showing high texture compared to the reduced texture of the PbCl2 films. Large lateral grain sizes were observed for the PbI2 films with a flat platelet grain morphology and an average grain size up to 734.2 ± 144.8 nm. PbCl2 films have columnar grains with an average grain size up to 386.7 ± 119.5 nm. The PbI2 films showed a band gap of about 2.4 eV, confirming its semiconducting properties, and the PbCl2 had a wide band gap of 4.3 eV, which shows the insulating properties of this material.

Microfluidic-integrated graphene optical sensors for real-time and ultra-low flow velocity detection

As microfluidic technology continues to mature, many techniques are being developed to monitor the flow of microfluidics. However, achieving breakthroughs in the real-time detection of ultra-low flow velocity and non-conductive liquid in microfluidic environments remains a major challenge. Here, microfluidic-integrated graphene optical sensorswith a sensitivity of 4.65 × 105 mV⋅s⋅m−1 and a detection limit of 4.9 × 10−5 m⋅s−1 were designed to address these challenges. We reported our efforts to quantify the impact of ultra-low flow velocity driven by ultra-small levels of pressure. A flow velocity of 3.7 × 10−4 m⋅s−1 was detected with a signal-to-noise ratio of approximately 7.5. A high-quality graphene layer that was directly grown on glass by an improved low-pressure chemical vapor deposition method and provided several advantages, including controllable thickness, high uniformity, high stability, and corrosion resistance. Graphene also has an excellent polarization-dependent effect. It was extremely sensitive to pressure-driven microfluidic flow because of the interaction between polarization light and the quartz glass/graphene film/medium multilayer-coupling structure, which fed back the signals in real-time. This novel sensor represents a breakthrough in the ultra-low level detection of the flow velocity of non-conductive microfluidics. We expect this sensor to have a broad array of applications in the field of microfluid velocity measurement.