Properties of Semiconductors: Electrodeposition, Gas Sensors, and PCB Devices

Created: February 6, 2018
Updated: December 17, 2020

Macro of Silicon wafers

I started working with gas sensors 10 years ago—my team had several ideas on how to improve the performance of our devices by integrating semiconductor nanomaterials into our PCB-based sensors. We were familiar with various electron, barrier heights, valence electrons, conduction band and the semiconductor interface. We were all masters of electrodeposition and masters of gas sensors in our own right, and we had the idea to integrate the two technologies. Wouldn’t you know, though, that a different kind of gas sensor would cause us all more trouble than anything the materials did.

One of the toilets had been phantom flushing for some time, and we decided, collectively, it would be an easy fix. Google said that it was probably just a leaky flapper, so we ordered the part and when it arrived started to the bathroom to take apart the toilet. Long story short, it took six masters of electrodeposition and gas sensors four hours to change this part on the toilet, but we definitely learned a bit about the internal workings of a toilet in the process.

Regardless of plumbing or PCB designing, it’s important for you to have a solid understanding of the medium you’re working in, and the tools you’ll be working with. Electro-depositing required materials directly into our PCB circuit enabled the continued miniaturization of our devices. Learning more about electrodeposition might be of service to you the next time you’re trying to find a seemingly impossible solution to a rigorous manufacturing demand.

Electrodeposition Properties: For Semiconductor Electronic Properties and Beyond

Electrodeposition, electro-plating—all of these methods are electrochemical processes that are used to deposit some material onto a substrate. Electrodeposition is an electrochemical process that can be used to form a variety of semiconductor films and nanostructures on conducting or semiconducting substrates. The precursor compounds are dissolved in a chemical bath, and the films deposit via an electrochemical reaction.

Certain nanostructures have unique optical and electronic properties that will enable development of new electronic devices. Integrating the nanoscale components with the supporting electronics is required if your unique piece of technology is to proliferate and become wildly successful.

Electrodeposition also enjoys other advantages over typical semiconductor deposition processes. The precursor materials tend to be less expensive, the process can be conducted in ambient conditions, and the equipment tends to cost less than physical or chemical vapor deposition (PVD or CVD), or plasma deposition systems. Electrodeposition also runs at low voltage in contrast to plasma deposition.

Barrel for electroplating equipment.
Oftentimes there are solutions you may have never considered for a voltage or current problem.

Mastering Electrodeposition and Other Cautions

Anyone that is new to this area should be warned: electrodeposition is easy to perform but difficult to master. Slight variations in the deposition conditions can drastically change the geometry and roughness of the resulting nanostructures. The primary factors influencing the structure of the resulting film are the pH of the chemical bath, its conductivity, temperature, the current density, and the presence of impurities.

Controlling the deposition conditions requires careful attention and practice. As some of the reactants are used up, the conductivity and pH can change thus resulting in a change in current density. Maintaining the conductivity and pH of the chemical bath requires continuously adding a small amount of electrolytic solution to the chemical bath while monitoring the pH and current density. This will help maintain the deposition conditions throughout the reaction.

Applications: Where Does This Knowledge Go?

One notable application can be drawn from the realm of biochemical sensors. Many electronic sensor platforms that are currently available are based on strain rheometry, surface acoustic wave (SAW) resonance shifts, or fluorescence spectroscopy. These devices see greater benefits by incorporating high aspect ratio nanostructures after perfecting electrodeposition processes to different semiconducting materials.

Take, for example, SAW sensors for detecting biological markers or hazardous chemicals. SAW biosensors typically use gold or silver nanoparticles with an attached ligand to detect their target analyte. The attached ligand binds to the analyte, and this increases the mass of the active sensing layer. If instead, a high aspect ratio semiconductor decorated with the metallic nanoparticles were used in these devices, the larger surface area preserves sensitivity while enhancing the detection range and usable lifetime of the device. More information on these devices can be found here.

Another example from this field relates to chemisorptive and physisorptive gas sensors. These devices typically use a polymer film deposited on a pair of interdigitated electrodes as the active sensing layer. If a nanowire film can be deposited directly on the electrodes, the increased surface area enhances both sensitivity and lifetime.

Set of sensors for various gas detections.
Gas sensors are just one of the many applications that you can innovate in your designs with.

Try Your Own Innovations

Integrating nanostructured components onto PCB boards via electrochemical techniques may be the first step required to bring new devices to market that have been typically relegated to the academic literature. These techniques also enable efficient control over the device footprint and allow designers to use unconventional and unique semiconductor material.

An electroplated PCB is an ideal substrate for integrating your piece of nanotechnology with conventional electronic components. The metal contacts on the PCB can easily take solder, which allows them to be integrated into larger scale devices and allows external components to be attached as needed. The metal contacts also form the substrate for electrodeposition of your semiconductor nanostructures.

If you’re looking to take your PCB designs to the next level, you’ll need PCB design software which can keep up with your own innovation. With a unified design environment, intuitive rule checking, smart manufacturing output files, and most importantly, a power distribution network for measuring your voltage and currents, Altium Designer® is capable of making your design software methodology make the transition from idea to innovation flawless.

To find out more about how to get the most effectiveness out of your PCB designs, consider talking to an expert at Altium today.

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