A PhD candidate requested the following information:
I would like to know some details about ‘the suspended monolayer graphene on cavities’:
If possible, could you provide more relevant information about this product?
Thank you for this new request. Please, find below the answers to your customer's questions:
Reference #222239 for specs and pricing.
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An associate professor of physics requested the following quote:
Looking for some semiconductor samples to have undergraduate students use scanning tunneling microscopy to look at the band gap at room temperature. I thought Gallium Arsenide would be a good option because they could cleave it with hand tools. I would also be interested in Si samples if they were pre-cut (to about 5mm x 5mm).
Can you confirm that these would still have a measurable band gap? The main objective for the students is to observe a band gap in the I-V curve using STM. High resistivity at the Fermi level would be fine. It’s okay if the band gap is less than that of undoped Si.
[Q1] Can you confirm that these would still have a measurable band gap?
[A1] As all semiconductor materials Si wafers have a band gap. I am sorry we cannot decide for you if you can measure with your method or not but the band gap exists for sure.
[Q2] High resistivity at the Fermi level would be fine. It’s okay if the band gap is less than that of undoped Si.
[A2] Yes, obviously the Fermi level in higher resistivity p-type wafers is deeper in the band gap and further from the conduction band than those undoped wafers.
Reference #263351 for specs and pricing.
The Fermi level of a material is an intrinsic property that depends on the electronic structure of the material, the temperature, and the presence of impurities (doping). For pure semiconductors and insulators at absolute zero, the Fermi level lies within the band gap, but its exact position varies with doping and other factors. Here's a general idea of where the Fermi level lies for the substrates you've mentioned:
Borofloat (Borosilicate Glass): As a type of glass, Borofloat is an insulator, not a semiconductor. Therefore, it doesn't have a Fermi level in the same way that semiconductors do. Its electronic structure is such that there is a large band gap, and the Fermi level would conceptually fall somewhere in the middle of this gap.
Glass: Ordinary glass, like Borofloat, is also an insulator with a large band gap. The Fermi level would again be within this band gap, not near the conduction or valence bands.
Silicon: Pure silicon at absolute zero has its Fermi level near the middle of the band gap. In doped silicon, the Fermi level can move closer to the conduction band (in n-type) or closer to the valence band (in p-type).
Gallium Arsenide (GaAs): For intrinsic (undoped) Gallium Arsenide, the Fermi level would be near the center of the band gap. In n-type GaAs, it would be closer to the conduction band, and in p-type, closer to the valence band.
Sapphire (Aluminium Oxide): Sapphire is an insulating material, so like glass, its Fermi level would theoretically lie in the middle of a wide band gap.
Silicon Carbide (SiC): The Fermi level of undoped Silicon Carbide is also located within the band gap. The exact position depends on the polytype of SiC (as it exists in different crystalline forms) and can be closer to the conduction band for n-type or the valence band for p-type.
It's important to note that these positions can only be approximated and will vary based on the material's purity, any doping agents introduced, and environmental conditions like temperature. In practical terms, the Fermi level is often determined experimentally rather than calculated theoretically for each specific sample of material.
The Fermi level is a concept from quantum physics that describes the energy level of electrons in a material. 
Think of it like the water level in a pool. If you have a lot of water, the water level is high. If you have a little water, the water level is low. In materials, electrons are like the water. They can have different energy levels, like steps in a pool.
The Fermi level is the topmost step that is covered by water (or has electrons) at absolute zero temperature, which is really, really cold. In a metal, the steps at the Fermi level are half-covered—meaning the electrons are just as likely to be there as not. It's important because it helps us understand how a material will conduct electricity or heat, and what will happen when we put different materials together.
If you think of a material as a hotel, the electrons are the guests and the rooms are the energy levels. The Fermi level is like the highest floor of the hotel where the guests are staying. At absolute zero temperature, there are no guests above this floor, but as you warm things up, some of the guests can have enough energy to visit higher floors (energy levels).
A doctoral student working in a materials research department asked for the follwoing fermi level information.
Could I ask if University Wafer produce the following item [n-type 4H-SiC, on axis (0001), Res.0.015~0.028ohm.cm; Research grade, 0.33 mm thick] my itself or outsourcing it to other companies (If so, could I ask which company it is?)
We purchased a few wafers from you and just wanted to know what the dopant concentration is + where the substrate is produced from. This matters for us in the context of divacancy qubit study as different producers in the market has different composition of the residual defects and Fermi level. If you could deliver the information about the dopant concentration and the chip maker, we would appreciate it.
UniversityWafer, Inc. quoted:
Yes! We can supply SiC Wafer 2'',3'' & 4''.
The dopant Nitrogen CC 1E18-19/cm3,the wafer from SICC
Reference #277893 for more specs and pricing.
Measuring the Fermi level of a substrate, which is the base layer that we put other materials on in things like electronics, can be pretty tricky, but here's a simplified explanation:
Using Contact with a Known Material: You can measure the Fermi level by touching the substrate with a material that has a well-known Fermi level, like a metal. When they touch, electrons will move between the two materials until their Fermi levels line up. This movement of electrons creates a voltage that we can measure with special tools. This voltage tells us the difference in energy between the two Fermi levels, and from that, we can figure out the Fermi level of the substrate.
Photoemission Spectroscopy: This is a fancy way to measure the energy of electrons. We shine light on the substrate, and the light knocks electrons out. By measuring the energy of these electrons, we can figure out the Fermi level. This method is like checking how much energy it takes to make the electrons leave their "home" level.
Field Effect: In a transistor, which is like a tiny electronic switch, we can apply an electric field to the substrate. This field changes the energy levels of the electrons. By observing how the current through the transistor changes when we apply different voltages, we can figure out the Fermi level of the substrate.
Kelvin Probe Force Microscopy: This is a super precise tool that can measure tiny changes in force between a tiny tip and the substrate. When the tip gets close to the substrate, it can feel the force from the electrons. By moving the tip around and measuring these forces very carefully, we can figure out the Fermi level across the surface of the substrate.
Scientists and engineers use these methods in high-tech labs to understand materials better and make things like solar panels, computer chips, and sensors work more efficiently.
A project assistant requested with the following question:
I want to ask you something about silicon wafer item 785. You mention that it's "Degenerate doped Si wafers". What do you mean by saying that? Do you mean that Fermi Level is closer to the valence band less than 3kT or something else? I am looking forward to hearing from you soon.
UniversityWafer, Inc. Answered:j
Yes, though the concept of a degenerately doped semiconductor is not a precise one. A degenerately doped semiconductor is one that is so heavily doped that it starts acting like a metal. A degenerately doped semiconductor is one with Nc<1E18/cc which corresponds to p-type Ro<0.040 or n-type Ro<0.020. At El-Cat we consider degenerately doped Silicon to have Ro<0.020 Ohmcm.
Reference #224057 for specs and pricing.
The Fermi level is the energy level at which the probability of finding an electron is 50% at absolute zero temperature. Here's how temperature affects the Fermi level:
At absolute zero (which is -273.15°C or 0 Kelvin), all electrons in a material fill up the lowest possible energy levels up to a certain point – this point is the Fermi level. Electrons are all packed in as tightly as possible, with no extra energy to move around.
As you increase the temperature from absolute zero, electrons start to get a little bit more energy from the heat. They can move to higher energy levels because they're getting excited by the heat. However, the actual position of the Fermi level doesn't change much with temperature. What changes is the distribution of electrons around it.
At higher temperatures, more electrons have enough energy to move to levels above the Fermi level. So, while the Fermi level itself is a fixed property of the material and doesn't shift much, the occupation of electrons at different energy levels around the Fermi level changes with temperature. This is because electrons follow a distribution law (called the Fermi-Dirac distribution) that becomes broader with increasing temperature, allowing more electrons to occupy higher energy states.
So, in summary, the Fermi level is a reference point that stays relatively constant, but the actual energy levels that electrons occupy will spread out more as the temperature rises.
In an n-type semiconductor, the Fermi level is located closer to the conduction band than to the valence band. Here's a simpler way to think about it:
Imagine a semiconductor as a two-story house. The bottom floor is the valence band, where most of the electrons live when they're not doing much. The top floor is the conduction band, where the electrons can move around and conduct electricity.
Now, n-type means we've added extra electrons to our semiconductor. It's like we've invited more people (electrons) to a party at the house, and the bottom floor is getting crowded. So some of these extra guests start hanging out on the stairs closer to the top floor because there's more room.
The Fermi level is like the average level where you'd find these extra guests. Because we've added more people, this average level is now closer to the top floor (the conduction band). So in an n-type semiconductor, the Fermi level is not in the middle of the house but shifted upwards towards the conduction band where the electrons have more energy and can move around more easily.
Fermi level pinning is kind of like when you play a game where you pin the tail on the donkey, but instead of a tail, it's the energy level of electrons, and instead of a donkey, it's a semiconductor.
Usually, in semiconductors, you can control where the energy level at which the electrons are most likely to be (that's the Fermi level) sits between the low-energy band (called the valence band) and the high-energy band (called the conduction band). By adding impurities or 'doping' the semiconductor, you can move the Fermi level up or down to make the material conduct electricity better or worse.
But sometimes, no matter how much you dope the semiconductor, the Fermi level doesn't move much. It's like it's stuck or 'pinned' in place. This happens because of states in the semiconductor that are right at the surface where it meets another material, like metal. These states can trap electrons or holes (which are the absence of electrons), and that makes it hard to move the Fermi level away from these states.
So, Fermi level pinning is like having a balloon that you want to move up or down, but it's tied to a chair. No matter how much you push or pull, it won't move much because it's pinned to the chair. In the same way, the Fermi level is pinned and doesn't move much because of these surface states. This can be really important for devices like transistors, where you need to control the Fermi level to get them to work right.