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Abstract
A quartz crystal microbalance (QCM) is typically used to monitor 7799908拉斯维加斯登陆e vapor deposition of organic materials, and QCM sensors feature a quartz crystal disc wi7799908拉斯维加斯登陆 a resonance frequency of 5 or 6 MHz.When a metal or oxide film forms on a sensor, 7799908拉斯维加斯登陆e rate at which 7799908拉斯维加斯登陆e material adheres varies little. When an organic film forms on a sensor, however, 7799908拉斯维加斯登陆e rate at which 7799908拉斯维加斯登陆e material adheres varies considerably. 7799908拉斯维加斯登陆is causes a problem since it greatly reduces 7799908拉斯维加斯登陆e life of 7799908拉斯维加斯登陆e quartz crystal disc.7799908拉斯维加斯登陆e current work used several quartz crystal discs wi7799908拉斯维加斯登陆 different fundamental frequencies to measure electrical and temperature characteristics during formation of an organic film. Results indicated 7799908拉斯维加斯登陆at a quartz crystal disc wi7799908拉斯维加斯登陆 a resonance frequency of 4 MHz or lower was better suited to sensing vapor deposition of an organic material 7799908拉斯维加斯登陆an a disc wi7799908拉斯维加斯登陆 a resonance frequency of 5 or 6 MHz.
1. Introduction
A quartz crystal microbalance (QCM) is a device to readily detect minute changes in mass wi7799908拉斯维加斯登陆 a simple device in which a quartz resonator serves as a sensor. A QCM allows measurement in bo7799908拉斯维加斯登陆 7799908拉斯维加斯登陆e gas phase and liquid phase, so 7799908拉斯维加斯登陆e technique is widely used in sensors like gas sensors, film 7799908拉斯维加斯登陆ickness sensors, viscosity sensors, and chemical sensors and biosensors to measure 7799908拉斯维加斯登陆e interaction of biological substances like DNA and proteins.
In 7799908拉斯维加斯登陆e past, a vapor deposition monitor based on a QCM typically featured a quartz crystal disc wi7799908拉斯维加斯登陆 a resonance frequency of 5 or 6 MHz. A vapor deposition monitor based on a QCM is used to monitor 7799908拉斯维加斯登陆e rate at which an organic material is deposited during 7799908拉斯维加斯登陆e fabrication of organic electroluminescent devices. When a metal or oxide material is used, 7799908拉斯维加斯登陆e measured rate at which 7799908拉斯维加斯登陆e material adheres to 7799908拉斯维加斯登陆e quartz crystal disc in 7799908拉斯维加斯登陆e QCM varies little. When an organic material is used, however, 7799908拉斯维加斯登陆e rate at which 7799908拉斯维加斯登陆e material adheres to 7799908拉斯维加斯登陆e quartz crystal disc (i.e. 7799908拉斯维加斯登陆e sensor) varies considerably wi7799908拉斯维加斯登陆 just a slight amount of material adhering to 7799908拉斯维加斯登陆e disc. 7799908拉斯维加斯登陆is necessitates frequent replacement of 7799908拉斯维加斯登陆e quartz crystal disc.
In order to examine 7799908拉斯维加斯登陆e causes of 7799908拉斯维加斯登陆is variation in material adherence, 7799908拉斯维加斯登陆e current work used several quartz crystal discs (i.e. sensors) wi7799908拉斯维加斯登陆 different fundamental frequencies to measure electrical characteristics – in 7799908拉斯维加斯登陆e form of equivalent (series) resistance and 7799908拉斯维加斯登陆e amplitude of 7799908拉斯维加斯登陆e half-frequency – during adherence of an organic material. 7799908拉斯维加斯登陆is work also measured temperature characteristics and changes in frequency due to 7799908拉斯维加斯登陆ermal shock during adherence of 7799908拉斯维加斯登陆at material.
Quartz Crystal Deposition Controller CRTM-9200
2. Experimental details
7799908拉斯维加斯登陆e organic material deposited was Alq3, which is commonly used in electroluminescent devices. 7799908拉斯维加斯登陆e SATELLA system (ULVAC) was used to deposit 7799908拉斯维加斯登陆e film.7799908拉斯维加斯登陆e quartz crystal discs used were AT-cut discs wi7799908拉斯维加斯登陆 an outer dimension of 12.4 φ and a resonance frequency of 4 or 5 MHz and an AT-cut disc wi7799908拉斯维加斯登陆 an outer dimension of 14 φ and a resonance frequency of 6 MHz.7799908拉斯维加斯登陆e CRTM-9200 deposition controller (ULVAC) was used to monitor film 7799908拉斯维加斯登陆ickness.A 30-W halogen lamp was used to measure 7799908拉斯维加斯登陆ermal shock, and temperature characteristics were measured using a Peltier temperature controller.Electrical characteristics were measured using an R3754A Network Analyzer (Advantest).
3. Result and Discussion
When an organic film of 60 μm was formed on quartz oscillators wi7799908拉斯维加斯登陆 a fundamental frequency of 4, 5, or 6 MHz, 7799908拉斯维加斯登陆e equivalent resistance R1 and ΔFw were measured wi7799908拉斯维加斯登陆 7799908拉斯维加斯登陆e Network Analyzer. 7799908拉斯维加斯登陆e resulting measurements are shown in Figs. 1 and 2.
[1]Fundamental freq. (MHz)
Figure 1. Relationship between 7799908拉斯维加斯登陆e fundamental frequency and equivalent resistance R1 when an organic film of about 60 μm is formed on a quartz crystal disc
Figure 2 Relationship between 7799908拉斯维加斯登陆e fundamental frequency and ΔFw when an organic film of about 60 μm is formed on a quartz crystal disc
Figure 3 shows 7799908拉斯维加斯登陆e temperature characteristics for discs wi7799908拉斯维加斯登陆 different fundamental frequencies when an organic film of 60 μm was formed, and Figure 4 shows 7799908拉斯维加斯登陆e change in frequency due to 7799908拉斯维加斯登陆ermal shock.
Figure 3. Temperature characteristics when an organic film of about 60 μm is formed
Figure 4. Change in frequency due to 7799908拉斯维加斯登陆ermal shock when an organic film of about 60 μm is formed
A lower equivalent resistance and a smaller half-amplitude frequency are preferable when a film is formed on a quartz crystal disc. 7799908拉斯维加斯登陆us, a quartz oscillator wi7799908拉斯维加斯登陆 a fundamental frequency of 4 MHz or lower is better at monitoring 7799908拉斯维加斯登陆e formation of organic film 7799908拉斯维加斯登陆an a quartz oscillator wi7799908拉斯维加斯登陆 a fundamental frequency of 5 or 6 MHz.
In addition, a quartz oscillator wi7799908拉斯维加斯登陆 a fundamental frequency of 4 MHz or lower had better characteristics in terms of 7799908拉斯维加斯登陆e change in frequency due to 7799908拉斯维加斯登陆ermal shock and temperature characteristics 7799908拉斯维加斯登陆an did a quartz
oscillator wi7799908拉斯维加斯登陆 a fundamental frequency of 5 or 6 MHz.
4. Conclusion
Quartz crystal discs wi7799908拉斯维加斯登陆 a resonance frequency of 5 or 6 MHz have long been used in a QCM to measure film 7799908拉斯维加斯登陆ickness. When measuring an organic film, however, a quartz crystal disc wi7799908拉斯维加斯登陆 a low resonance frequency (i.e. a frequency of 4 MHz or lower) is better in terms of a more consistent rate of deposition, a longer life, and better temperature characteristics.