Influence of Crystalline Microstructure on Optical Response of Single ZnSe Nanowires
Bibliographic record
Abstract
Semiconductor nanowires (NWs) are anticipated to play a crucial role in future electronic and optoelectronic devices. Their practical applications remain hindered by an urging need for feasible strategies to tailor their optical and electronic properties. Strategies based on strain and alloying are limited by issues such as defects, interface broadening and alloy scattering. In this thesis, a novel method to engineer the optoelectronic properties based on strain-free periodic structural modulations in chemically homogeneous Nanowire Twinning Superlattices (NTSLs) is experimentally demonstrated. NTSLs are an emerging new class of nanoscale material, composed of periodically arranged rotation twin-planes along the length of NWs. The main objective of this thesis is to establish the relationship between the electronic energy band gap (Eg) and the twin-plane spacing (d) in NTSLs, quantified using a periodicity parameter, based on ZnSe. ZnSe was chosen because of its excellent luminescence properties, and potential in fabrication of optoelectronic devices in the near-UV and blue region of the spectrum. \nA prerequisite to establishing this correspondence is a prior knowledge of the photoluminescence (PL) response and the nature of fundamental optical transitions in defect-free single crystal ZnSe NWs with zinc-blende (ZB) and wurtzite (WZ) crystal structures. There has been no systematic work done yet on understanding these fundamental optical processes, particularly on single NWs and in relation to their crystalline microstructure. Therefore, the secondary objective of this thesis is to study the influence of native point defects on the optical response of single ZnSe NWs in direct relation to their crystalline microstructure. \nThe PL response from single ZB and WZ NWs was determined unambiguously, and excitonic emission linewidths close to 1 meV were observed, which are the narrowest reported linewidths thus far on ZnSe NWs. Based on this and extensive optical and structural characterization on individual NTSLs, a linear variation in Eg is shown through a monotonic shift in PL peak position from ZnSe NTSLs as a function of d, with Eg's that lie between those of ZB and WZ crystal structures. This linear variation in Eg was also validated by ab Initio electronic structure calculations. This establishes NTSLs as new nanoscale polytypes advantageous for applications requiring tunable band gaps.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".