Podcast
Questions and Answers
What is the main principle that allows electrons to tunnel through a barrier in scanning tunneling microscopy?
What is the main principle that allows electrons to tunnel through a barrier in scanning tunneling microscopy?
Which of the following materials is suitable for investigation using scanning tunneling microscopy?
Which of the following materials is suitable for investigation using scanning tunneling microscopy?
What creates the electric current measured as tunneling current in a scanning tunneling microscope?
What creates the electric current measured as tunneling current in a scanning tunneling microscope?
Which part of the scanning tunneling microscope is responsible for producing a topographic map of the surface?
Which part of the scanning tunneling microscope is responsible for producing a topographic map of the surface?
Signup and view all the answers
What is the significance of the year 1986 in the context of scanning tunneling microscopy?
What is the significance of the year 1986 in the context of scanning tunneling microscopy?
Signup and view all the answers
Which property of electrons allows them to be visualized and manipulated using scanning tunneling microscopy?
Which property of electrons allows them to be visualized and manipulated using scanning tunneling microscopy?
Signup and view all the answers
What technology was advanced through the invention of the scanning tunneling microscope?
What technology was advanced through the invention of the scanning tunneling microscope?
Signup and view all the answers
In what way can deposition of electrons be observed using scanning tunneling microscopy?
In what way can deposition of electrons be observed using scanning tunneling microscopy?
Signup and view all the answers
What is one of the main applications of STM in materials science?
What is one of the main applications of STM in materials science?
Signup and view all the answers
Which achievement was made in STM in 2000?
Which achievement was made in STM in 2000?
Signup and view all the answers
What does STM help researchers understand regarding catalysis?
What does STM help researchers understand regarding catalysis?
Signup and view all the answers
How is the tunneling current affected by the distance between the tip and the specimen?
How is the tunneling current affected by the distance between the tip and the specimen?
Signup and view all the answers
In constant-current mode, what happens when the tunneling current increases?
In constant-current mode, what happens when the tunneling current increases?
Signup and view all the answers
What is the resolution limit of STM when mapping the arrangement of atoms on a surface?
What is the resolution limit of STM when mapping the arrangement of atoms on a surface?
Signup and view all the answers
Which related technique was developed alongside STM for imaging purposes?
Which related technique was developed alongside STM for imaging purposes?
Signup and view all the answers
What happens to the tunneling current when the tip is over a bump of an atom?
What happens to the tunneling current when the tip is over a bump of an atom?
Signup and view all the answers
Study Notes
Scanning Tunneling Microscopy (STM)
- Invented by Gerd Binnig and Heinrich Rohrer in 1986, receiving a Nobel Prize.
- Based on quantum tunneling, where electrons penetrate regions classically forbidden.
- Substances under investigation must be electrically conductive (e.g., copper).
- Inner shell electrons are tightly bound.
- Outer shell (valence) electrons are loosely bound, forming an electron gas.
- Atomic nuclei and inner shell electrons have a net positive charge and arrange in a lattice.
- Classical physics: Electrons as particles need sufficient energy to overcome the barrier.
- Quantum tunneling: Electrons as waves can tunnel through the barrier.
- STM construction: Metal probe with a fine tip (single atom), positively charged, above the surface.
- Gap between probe tip and surface is finely adjusted (a few tenths of a nanometer).
- Tunneling current (electric current) is measured as electrons tunnel across the gap.
- Current stays constant as tip scans across the surface.
- Topographic map is created from the probe tip's up-and-down motion as it scans.
- This map reveals individual atoms and molecules.
- Atomic-scale imaging enables studying surface structures and properties.
- Surface manipulation is possible by moving atoms and molecules.
STM Applications
- Enables the study of surface reactions and catalytic processes.
- Used to study materials properties (conductivity, magnetism, superconductivity).
- Crucial for building and characterizing nanostructures (nanotubes, nanowires, and nanoparticles).
- Can image biological samples (DNA, proteins, and cells) in their natural environment.
STM History
- Invented in 1981 at IBM Zurich.
- First commercial STMs released in 1986.
- Widely used in research by the 1990s.
- Advancements in resolution and speed continued into the 2000s.
- New techniques (like nc-AFM) were developed to complement STM.
STM Operation
- Current generated is nano-sized (few tenths of a nanoampere).
- Probability of tunneling decreases rapidly with increasing tip-to-specimen distance.
- Even 0.01 nm separation causes noticeable changes in tunneling current.
- Scanning across a surface causes continuous changes in tunneling current.
- Current is higher when the tip is above a bump (feature) and lower when it's in a valley (feature).
- Constant-current mode (CCM): Computer constantly adjusts tip height/position to maintain constant tunneling current.
- Tip moves up/down to maintain constant current throughout the scan.
Other STM achievements and features
- Imaging individual atoms (1982).
- Manipulating individual atoms (1990).
- Creating artificial molecules (2000).
- Observing chemical reactions at atomic level (2007).
- Control is done by mounting the probe on 3 tiny ceramic posts (which change position/stretch when voltage changes).
- Piezoelectric materials respond to voltage by changing shape (or to deformation by generating voltage).
- Recording height at different points creates a topographic map.
- Used for imaging and creation of nanostructures.
Studying That Suits You
Use AI to generate personalized quizzes and flashcards to suit your learning preferences.
