UROP-Poster-Final
1
Contact Angle Measurements Acknowledgments Hydrophobic Substrate Patterning David Barton , Anna Swan Boston University, Electrical and Computer Engineering, 8 St. Mary’s St, Boston, MA Contact: [email protected] • This work was funded by Boston University’s Undergraduate Research Opportunities Program (UROP) and the National Science Foundation’s Division of Materials Research (NSF DMR) 1411008. • Thanks to Bruker for the AFM images. Special thanks to Anlee Krupp, Paul Mak, Xuanye Wang, Jason Christopher, Bennett Goldberg, and Anna Swan for all their time and support. Interface Between regions Strain engineering is the process of changing the physical properties of a material by applying strain. To lay the groundwork for measuring strain, it is necessary to pattern a substrate to have varying coefficients of friction. This was accomplished by altering the substrate’s hydrophobicity. In theory, the more hydrophobic the substrate, the less friction a two-dimensional (2D) crystal will experience, as this is due to a decrease in the van der Waals forces between the crystal and the substrate. The patterning of the substrates was achieved through the use of photolithography and atmospheric chemical vapor deposition (CVD) of a silane called octadecyltrimethoxysilane (OTMS). Photolithography is the process of using light to transfer geometric patterns to a substrate covered in a photopatternable chemical called a photoresist. Atmospheric CVD is the process used to deposit a thin film of gaseous OTMS at atmospheric pressure in order to alter the substrate’s hydrophobicity. Not only did the OTMS increase the substrate’s hydrophobicity, but it was also experimentally verified to be photodegradable. This infers that the OTMS can be degraded with shorter wavelength UV light, meaning that the hydrophobicity of the OTMS- coated substrate would decrease as the substrate is exposed to more UV light. Thus, the combination of these processes will aid in discovering intrinsic properties of 2D crystals such as graphene, MoS 2 , and hBN. These materials may one day be used in various applications such as touch-screen technology, LEDs, and improved solar cells. • A basic patterning procedure for creating varying areas of friction on a substrate through hydrophobic manipulation was achieved. • In order to create these patterns, it is necessary to perform photolithography, then atmospheric CVD of a silane (OTMS works very well), and to clean the substrate to ensure optimal conditions for eventual transfers of 2D crystals. • UV degradation was explored for future manipulation of the difference in hydrophobicity between the silanized and non-silanized sections. • Macroscale patterns were sufficiently studied through optical measurements of contact angle as well as through water coverage. • Microscale patterns require AFM measurements to determine the sharpness of the interface between the two regions with and without silane. • The next steps in the microscale patterning include verifying that silane was successfully deposited as well as determining its locations with an AFM. • Photolithography : This procedure contains the following steps: pre-baking, spinning of photoresist, post-baking, exposure, and development. • Atmospheric CVD : Liquid silane is heated into a gaseous form, and deposited onto the substrate. This is also known as silanization. • Cleaning : The substrate is sonicated in acetone and isopropanol, and blow-dried with nitrogen. A piranha cleaning may be performed as well. • UV Degradation : 190nm wavelength UV light is used to degrade the silane covering the substrate. OTMS was used as it is photodegradable. • Contact Angle Measurements : All contact angle (CA) measurements are taken with a contact angle goniometer. • Atomic Force Microscopy (AFM) : An atomic force microscope is used to detect sub-nanometer height differences on the surface of a substrate. ~10º ~50º ~100º Macroscale Patterning Microscale Patterning UV Degradation Semi-circles Quarter-circles Image of Photomask Image of Photomask Implementation on Substrate Implementation on Substrate Photomask Substrate Photomask Substrate vs. vs. Abstract Methods Patterned with Photoresist Covered with Water Before CVD After CVD and Sonication Patterned with Photoresist After CVD and Sonication After Piranha Cleaning Using Atomic Force Microscopy To Locate Silane Patterns • The substrate patterned into quadrants demonstrates the patterning accuracy. • The substrate patterned into halves demonstrates the difference in hydrophobicity between the silanized and non- silanized sections. Performing a piranha cleaning alters the contact angles of each section, but the difference in contact angle appears to be maintained. Lateral Force Microscopy (Contact Mode) (These images are courtesy of Bruker.) Optical Measurement Non-silanized Silanized • It is possible to determine the locations of microscopic patterns of silane due to the step height between the silanized and non-silanized sections of the substrate. • Microscale patterns were achieved, but more adjustments need to be made to ensure maximum conformity. Conclusions Increasing Hydrophilicity Increasing Hydrophobicity Before CVD
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Transcript of UROP-Poster-Final
Contact Angle Measurements
Acknowledgments
Hydrophobic Substrate PatterningDavid Barton, Anna Swan
Boston University, Electrical and Computer Engineering, 8 St. Mary’s St, Boston, MA
Contact: [email protected]
• This work was funded by Boston University’s Undergraduate Research Opportunities Program (UROP) and the National Science Foundation’s Division of Materials Research (NSF DMR) 1411008.
• Thanks to Bruker for the AFM images. Special thanks to Anlee Krupp, Paul Mak, Xuanye Wang, Jason Christopher, Bennett Goldberg, and Anna Swan for all their time and support.
Interface Between regions
Strain engineering is the process of changing the physical properties of a material by applying strain. To lay the groundwork for measuring strain, it is necessary to pattern a substrate to have varying coefficients of friction. This was accomplished by altering the substrate’s hydrophobicity. In theory, the more hydrophobic the substrate, the less friction a two-dimensional (2D) crystal will experience, as this is due to a decrease in the van der Waals forces between the crystal and the substrate. The patterning of the substrates was achieved through the use of photolithography and atmospheric chemical vapor deposition (CVD) of a silane called octadecyltrimethoxysilane (OTMS). Photolithography is the process of using light to transfer geometric patterns to a substrate covered in a photopatternable chemical called a photoresist. Atmospheric CVD is the process used to deposit a thin film of gaseous OTMS at atmospheric pressure in order to alter the substrate’s hydrophobicity. Not only did the OTMS increase the substrate’s hydrophobicity, but it was also experimentally verified to be photodegradable. This infers that the OTMS can be degraded with shorter wavelength UV light, meaning that the hydrophobicity of the OTMS-coated substrate would decrease as the substrate is exposed to more UV light. Thus, the combination of these processes will aid in discovering intrinsic properties of 2D crystals such as graphene, MoS2, and hBN. These materials may one day be used in various applications such as touch-screen technology, LEDs, and improved solar cells.
• A basic patterning procedure for creating varying areas of friction on a substrate through hydrophobic manipulation was achieved.
• In order to create these patterns, it is necessary to perform photolithography, then atmospheric CVD of a silane (OTMS works very well), and to clean the substrate to ensure optimal conditions for eventual transfers of 2D crystals.
• UV degradation was explored for future manipulation of the difference in hydrophobicity between the silanized and non-silanized sections.
• Macroscale patterns were sufficiently studied through optical measurements of contact angle as well as through water coverage.
• Microscale patterns require AFM measurements to determine the sharpness of the interface between the two regions with and without silane.
• The next steps in the microscale patterning include verifying that silane was successfully deposited as well as determining its locations with an AFM.
• Photolithography: This procedure contains the following steps: pre-baking, spinning of photoresist, post-baking, exposure, and development.
• Atmospheric CVD: Liquid silane is heated into a gaseous form, and deposited onto the substrate. This is also known as silanization.
• Cleaning: The substrate is sonicated in acetone and isopropanol, and blow-dried with nitrogen. A piranha cleaning may be performed as well.
• UV Degradation: 190nm wavelength UV light is used to degrade the silane covering the substrate. OTMS was used as it is photodegradable.
• Contact Angle Measurements: All contact angle (CA) measurements are taken with a contact angle goniometer.
• Atomic Force Microscopy (AFM): An atomic force microscope is used to detect sub-nanometer height differences on the surface of a substrate.
~10º ~50º ~100º
Macroscale Patterning
Microscale Patterning
UV Degradation
Semi-circles Quarter-circles
Image of Photomask Image of Photomask
Implementation on Substrate Implementation on Substrate
Photomask Substrate Photomask Substrate
vs. vs.
Abstract
Methods
Patterned with Photoresist Covered with Water
Before CVD After CVD and Sonication
Patterned with Photoresist After CVD and Sonication After Piranha Cleaning
Using Atomic Force Microscopy To Locate Silane Patterns
• The substrate patterned into quadrants demonstrates the patterning accuracy.
• The substrate patterned into halves demonstrates the difference in hydrophobicity between the silanized and non-silanized sections. Performing a piranha cleaning alters the contact angles of each section, but the difference in contact angle appears to be maintained.
Lateral Force Microscopy (Contact Mode)
(These images are courtesy of Bruker.)
Optical Measurement
Non-silanized Silanized
• It is possible to determine the locations of microscopic patterns of silane due to the step height between the silanized and non-silanized sections of the substrate.
• Microscale patterns were achieved, but more adjustments need to be made to ensure maximum conformity.
Conclusions
Increasing Hydrophilicity Increasing Hydrophobicity
Before CVD
