Method, system and sensor for analysing a sample, and process for manufacturing an electrode

A system for analysing a sample comprising a layer having a first interface and a second interface, the system comprising:

• a sensor, the sensor comprising a pulsed source of terahertz radiation adapted to irradiate the sample with a pulse of terahertz radiation, said pulse comprising a plurality of frequencies in the range from 0.01 THz to 10 THz, and a detector for detecting reflected radiation to produce a sample waveform, said sample waveform being derived from the reflected radiation;
• and an analysis unit, said analysis unit comprising a processor and a memory, said processor adapted to:
• obtain a first reflection waveform from the sample waveform, the first reflection waveform corresponding to the reflection from the first interface;
• obtain a second reflection waveform from the sample waveform, the second reflection waveform corresponding to the reflection from the second interface;
• compare the first reflection waveform with the second reflection waveform to produce an estimate of a thickness and a complex refractive index of the layer;
• produce a synthesised signal using the estimate of the thickness and complex refractive index;
• vary at least one of the thickness and complex refractive index to reduce an error between the sample waveform and the synthesised signal;
• and
• output the thickness of the layer.

A method for adapting a system for analysing a sample comprising a layer having a first interface and a second interface, the system comprising a sensor, the sensor comprising a pulsed source of terahertz radiation adapted to irradiate the sample with a pulse of terahertz radiation, said pulse a plurality of frequencies in the range from 0.01 THz to 10 THz, a detector for detecting reflected radiation, and an optical element,

• the method comprising:
• obtaining an estimate of the refractive index of the layer;
• obtaining an estimate of the thickness of the layer;
• and
• determining a f-number of the optical element such that the confocal parameter, scaled by the estimate of the refractive index, is greater than the estimate of the thickness of the layer.

A sensor for analysing a sample comprising a layer having a first interface and a second interface, the sensor comprising:

• a pulsed source of terahertz radiation adapted to generate a pulse of terahertz radiation, said pulse comprising a plurality of frequencies in the range from 0.01 THz to 10 THz;
• a focussing element configured to direct the generated pulse of terahertz radiation towards a sample using a first path, and to direct the pulse of terahertz radiation towards an internal mirror using a second path;
• and,
• a detector for detecting reflected radiation to produce a sample waveform, wherein the sample waveform comprises radiation reflected from the sample via the first path, and radiation reflected from the internal mirror via the second path.