In situ scanning tunneling microscopy of InAs quantum dots on GaAs( 0 0 1 ) during molecular beam epitaxial growth
Abstract Arrays of InAs quantum dots (QDs) have been studied using in situ scanning tunneling microscopy (STM) during their growth by molecular beam epitaxy on GaAs(0 0 1). At a substrate temperature of 400 °C under As 4 flux, both the QDs and the underlying step-terrace structure of the wetting layer (WL) are found to be static, with neither step-flow nor QD ripening observed. Higher resolution images of the mature WL show slightly different [1 1 0] periodicities to those observed in quenched STM studies.
Heteroepitaxial growth of InAs on GaAs(001) by in situ STM located inside MBE growth chamber
The growth of InAs on GaAs(001) is of great interest primarily due to the self-assembly of arrays of quantum dots (QDs) with excellent opto-electronic properties. However, a basic understanding of their spontaneous formation is lacking. Advanced experimental methods are required to probe these nanostructures dynamically in order to elucidate their growth mechanism. Scanning tunneling microscopy (STM) has been successfully applied to many GaAs-based materials grown by molecular beam epitaxy (MBE). Typical STM-MBE experiments involve quenching the sample and transferring it to a remote STM chamber under arsenic-free ultra-high vacuum. In the case of GaAs-based materials grown at substrate temperatures of 400-600^oC, operating the STM at room temperature ensures that the surface is essentially static on the time scale of STM imaging. To attempt dynamic experiments requires a system in which STM and MBE are incorporated into one unit in order to scan in situ during growth. Here, we discuss in situ STM results from just such a system, covering both QDs and the dynamics of the wetting layer.
Atiyah's Introduction to the Law of Contract
1. Introduction 2. Definition and Classification PART I: FORMATION OF CONTRACTS 3. Offer and Acceptance 4. Beyond Offer and Acceptance: Formalities, Intent to Create Legal Relations, and Consideration PART II: THE CONTENT OF THE CONTRACT 5. Express Terms 6. Implied Terms 7. The Force and Scope of Contractual Obligations: Standards of Care, Mistake, Frustration, Breach, and Notice 8. Unenforceable Contracts and Terms PART III: EXCUSES FOR NON-PERFORMANCE 9. The Duty to Disclose Material Facts 10. Misrepresentation 11. Duress and Undue Influence 12. Unfair Contracts PART IV: ENFORCING THE CONTRACT 13. Third Party Rights 14. Remedies For Breach of Contract