# Questions tagged [semiconductor]

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### Fermi energy lower than valence band maximum?

I am trying to analyze the density of electronic states of a $\ce{TiO2}$ slab, but the result I got from VASP shows the fermi energy is lower than the valence band maximum (VBM) by a small energy ...
• 2,057
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### Which software to model Fermi level position of graphene in an external electric field?

I want to model a graphene layer that is sandwiched in a pn junction under bias (the current flows orthogonal to the graphene layer). According to what I've found in literature graphene can be treated ...
• 61
83 views

### Validity of estimating electron relaxation time using the smallest cross section of a structure [closed]

I am studying nano-scale constrictions in semiconductor materials. Imagine two nano-particles joined together by a single point of crystalline contact to look like an hour-glass filled with sand. ...
• 2,653
124 views

### Can a material be a conductor in one direction and a semiconductor in another direction?

I know that semiconductors have a band gap, and conductors have bands that cross the Fermi level. However, can a material have a band gap for certain $\vec k$ regions but bands cross the Fermi level ...
118 views

### Effect of carrier concentration on electrical conductivity

As per my understanding, the electrical conductivity of a material can be expected to increase with the increased carrier concentration. However, beyond a certain (extreme) point, the electrical ...
• 2,653
690 views

### Cohesive Energy of a metal oxide

I am trying to calculate the cohesive energy of certain metal oxides. However, I am only able to find a formula that is applicable to systems with a single element (say $\ce{Cu}$ metal or $\ce{Si}$ ...
• 991
503 views

### What does it mean if the Fermi level crosses into the valence band? How about into the conduction band?

Just recently got into DFT and I've been doing a few calculations on my own on Quantum Espresso. I've come up with electronic band structures for materials that I've been looking at and I was hoping ...
• 171
90 views

### How to interpret defect formation energy diagram?

Why are formation energy diagrams typically plotted as a function of Fermi energy, and how should one interpret the changes in the x-axis before the charge state changes in these diagrams? Figure ...
31 views

### Optimal Manufacturing Process for a Device [closed]

I am designing a device that has tiny etched gratings (shown in red) in the silicon substrate, with various structures on either side of it (shown in green). I am wondering what the ideal way would be ...
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