阅读说明：本技术 一种用于评估高反射率膜损耗稳定性的测试方法 (Test method for evaluating loss stability of high-reflectivity film ) 是由 曾慧中 杨潇 幸代鹏 张文旭 张万里 于 2019-09-04 设计创作，主要内容包括：本发明属于材料测试技术领域,具体涉及了一种用于评估高反射率膜损耗稳定性的X射线辐照测试方法。本发明利用X射线的电荷积累效应,模拟高反膜因荷电积累的失效过程：采用的X射线源对高反膜表面进行荷电处理,在累积的处理过程中；同时利用光电子能谱仪原位监测高反膜表面化学态的变化,间断的进行XPS分析,检测高反膜表面的各元素的化学态变化。通过对随机选取的失效组样品和非失效组样品进行统计分析,并引入α和β参数描述O1s峰的对称性,只用到了两个拟合参数,就可以评估辐照荷电老化时的损耗变化,便于工程实际应用,是一种方便、快捷的判别方法。特别适合用于膜层材料工艺实验的快速优化、工艺监控等环节。(The invention belongs to the technical field of material testing, and particularly relates to an X-ray irradiation testing method for evaluating loss stability of a high-reflectivity film. The invention utilizes the charge accumulation effect of X-ray to simulate the failure process of the high-reflection film due to charge accumulation: carrying out charge treatment on the surface of the high-reflection film by using an X-ray source in an accumulated treatment process; meanwhile, the change of the chemical state of the surface of the high-reflection film is monitored in situ by a photoelectron spectrometer, XPS analysis is carried out discontinuously, and the change of the chemical state of each element on the surface of the high-reflection film is detected. By carrying out statistical analysis on failure group samples and non-failure group samples which are randomly selected and introducing alpha and beta parameters to describe the symmetry of an O1s peak, only two fitting parameters are used, the loss change during irradiation charge aging can be evaluated, the practical application of engineering is facilitated, and the method is a convenient and rapid discrimination method. The method is particularly suitable for links such as rapid optimization, process monitoring and the like of a film material process experiment.)

1. A test method for evaluating loss stability of a high-reflectivity film comprises the following specific steps:

step 1: carrying out initial-state XPS (XPS) spectrum collection on a reverse film to be measured in height;

step 2: after the spectrum is collected, closing a neutralizer of the XPS equipment, and irradiating the sample for 2-7 minutes by X-rays carried by the equipment to ensure that the charge is accumulated on the surface of the high-reflection film;

and step 3: after the irradiation is finished, starting a neutralizer immediately, and carrying out XPS test on the irradiated high-reflection film;

and 4, step 4: repeating the steps 2 and 3, and performing total 2-7 times of irradiation and 3-8 times of XPS test on the high-reflection film;

and 5: analyzing the XPS photoelectron spectrum of all the obtained high-reflectivity film samples to be detected, and analyzing the shape change of the O1s peak before and after irradiation, wherein the loss of the sample with poor symmetry of the O1s peak is large;

step 6: carrying out Gaussian-Lorentz type GL30 fitting on an O1s peak, and introducing alpha and beta parameters to describe the component symmetry of a Gaussian-Lorentz function;

when α ═ β ═ 1.0, the peak shape is a standard symmetrical peak, and when α or β deviates from 1.0, a difference in the symmetry of the peak shape occurs. Wherein the sizes of alpha and beta respectively correspond to the degrees of symmetrical Gaussian-Lorentz peaks of the deviation of peak shapes at the left side and the right side of O1 s; the peak shape function LA is in mathematical form

Where L is the standard Gaussian-Lorentz function, f is the full width at half maximum FWHM of the peak, e is the center position of the peak, and x is the XPS spectrum Binding Energy.

And 7: the loss of the high reflection film to be detected is evaluated by using the fitting parameters alpha and beta of the XPS spectrogram of the sample to be detected after irradiation, the sample with better symmetry, namely the alpha and the beta are between 1.0 and 1.1, the loss stability is better, the change is less than 35ppm, the alpha and the beta of the sample with poor symmetry deviate from 1.0, the loss stability is poorer, and the change is more than 35 ppm.

Technical Field

The invention belongs to the technical field of material testing, and particularly relates to an X-ray irradiation testing method for evaluating loss stability of a high-reflectivity film.

Background

The loss of the high-reflectivity film (high-reflectivity film for short) is generally lower than 100ppm (100 x 10)^-6) The optical fiber is one of the key components of laser systems such as a laser, a laser gyro, a gravitational wave detector and the like. The high-reflection film is actually a multi-layer dielectric film, so that the reflectivity of the high-reflection film is more than 99.9999%. The application environment of the high-reflection film is complex, the loss can decay along with the service time, and the loss stability of the high-reflection film is an important index for evaluating the performance of the high-reflection film.

At present, a method for measuring the loss stability of a high-reflection film is a light attenuation method, namely, laser pulses are guided into an optical cavity through an optical axis, the laser pulses are reflected back and forth between two reflectors to form oscillation, and a detector detects the attenuation process of the laser pulses. How to rapidly evaluate the loss stability of the high-reflection film becomes an important work for rapidly optimizing the high-reflection film material and structure.

Disclosure of Invention

Aiming at the problems or the defects, the invention provides a test method for evaluating the loss stability of a high-reflectivity film, which aims to solve the problems that the conventional high-reflectivity film loss stability measurement method is complex in operation, cannot perform real-time original taste test and consumes long time.

The specific technical scheme is as follows:

step 1: carrying out initial-state XPS (XPS) spectrum collection on a reverse film to be measured in height;

step 2: after the spectrum is collected, closing a neutralizer of the XPS equipment, and irradiating the sample for 2-7 minutes by X-rays carried by the equipment to ensure that the charge is accumulated on the surface of the high-reflection film;

and step 3: after the irradiation is finished, starting a neutralizer immediately, and carrying out XPS test on the irradiated high-reflection film;

and 4, step 4: repeating the steps 2 and 3, and performing total 2-7 times of irradiation and 3-8 times of XPS test on the high-reflection film;

and 5: analyzing the XPS photoelectron spectrum of all the obtained high-reflectivity film samples to be detected, and analyzing the shape change of the O1s peak before and after irradiation, wherein the loss of the sample with poor symmetry of the O1s peak is large;

step 6: a Gaussian-Lorentz line-type (GL30) fit was performed on the O1s peak and alpha and beta parameters were introduced to describe the fractional symmetry of the Gaussian-Lorentz function.

When α ═ β ═ 1.0, the peak shape is a standard symmetrical peak, and when α or β deviates from 1.0, a difference in the symmetry of the peak shape occurs. Wherein, the sizes of alpha and beta respectively correspond to the degrees of symmetrical Gaussian-Lorentz peaks of the deviation of the peak shapes of the left side and the right side of O1 s. The peak shape function (LA) is in mathematical form

Where L is the standard Gaussian-Lorentz function, f is the full width at half maximum (FWHM) of the peak, e is the center position of the peak, and x is the XPS spectrum Binding Energy.

And 7: the loss of the high reflection film to be detected is evaluated by using the fitting parameters alpha and beta of the XPS spectrogram of the sample to be detected after irradiation, the sample with better symmetry, namely the sample with alpha and beta between 1.0 and 1.1 has better loss stability and less change than 35ppm, and the sample with poor symmetry (the sample with alpha and beta deviating from 1.0) has poorer loss stability and more change than 35 ppm.

The method utilizes the charge accumulation effect of X-rays to simulate the failure process of the high-reflection film due to charge accumulation. And the X-ray photoelectron spectrometer is adopted to realize X-ray induced charge accumulation, and the photoelectron spectrometer is utilized to monitor the change of the surface chemical state of the high-reflectivity film in situ. When the surface chemical state is monitored, the XPS charge neutralization system needs to be closed, and then the ray source is started. And (3) carrying out charge treatment on the surface of the high-reflection film by adopting an X-ray source, and intermittently carrying out XPS analysis in the accumulated treatment process to detect the chemical state change of each element on the surface of the high-reflection film. Statistical analysis of randomly selected samples from the failure group (loss increase greater than 35ppm) and samples from the non-failure group showed that the symmetry of the O1s peak in the high-reflection film correlated with the loss increase of the high-reflection film.

A traditional XPS analysis O1s peak uses multimodal fitting, a multilayer medium high-reflection film O1s peak uses multimodal fitting to be an adsorbed oxygen peak, a combined oxygen peak and an oxygen vacancy peak in sequence, the fitting peak needs to be described by a peak center Position (Position), a full width at half maximum (FWHM) and a peak Area (Area), multimodal fitting parameters are multiple and are not beneficial to rapid evaluation, in order to solve the problem, alpha and beta parameters are introduced to describe the symmetry of the O1s peak, only two fitting parameters are used, loss change during irradiation charge aging can be evaluated, engineering practical application is facilitated, and the method is a convenient and rapid discrimination method. The method is particularly suitable for links such as rapid optimization, process monitoring and the like of a film material process experiment.

In conclusion, the invention provides a simple and real-time in-situ high-reflection film loss stability measuring method.

Drawings

FIG. 1 is a typical XPS spectrum of a sample of a high reflectance film of an example;

FIG. 2 shows a significant change in XPS spectra of the O1s peak of a typical sample before and after irradiation charging of the examples;

FIG. 3 is a graph of the number of exposures of samples with stable and unstable losses versus samples α and β for the examples;

FIG. 4 is a graph of example empirical indices α, β versus increase in high film loss.

Detailed Description

The invention is further illustrated by the following figures and examples:

a multi-layer medium high-reflection film sample is subjected to X-ray irradiation, and the chemical state change of the film after the surface charge is analyzed by XPS.

The specific experimental method comprises the following steps:

firstly, carrying out initial state XPS (X-ray diffraction) spectrum collection on a high-reflectivity film sample, wherein the spectrum comprises a full spectrum and high-resolution carbon element (C1s), an oxygen element (O1s) and a silicon element spectrum (Si2 p);

secondly, after the spectrum is collected, closing a neutralizer of the XPS equipment, and irradiating the sample for 5 minutes by X-rays carried by the equipment to ensure that the charge is accumulated on the surface of the high-reflectivity film;

thirdly, immediately starting a neutralizer after the irradiation is finished, carrying out XPS test on the irradiated high-reflection film, and repeating the spectrum collecting process; then repeating the previous two steps, and carrying out 4 times of irradiation and 5 times of XPS test on the high-reflection film;

fourthly, performing XPS photoelectron spectroscopy: firstly, carrying out spectrum correction on an adsorbed carbon element (C1s) compared with a standard 284.8eV spectrum; subsequently, the oxygen element (O1s) and the silicon element (Si2p) were subjected to a spectrum analysis.

The results of the X-ray accelerated irradiation experiments of the exemplary high-reflectivity film sample of this example are shown in fig. 1. FIG. 1 is a diagram of a silicon element and an oxygen element of a sample with a diagram symmetry change. The measured spectrum after the irradiation times increased is shown from bottom to top in the figure. By analyzing the XPS spectrum, the high-reflection film sample with the silicon element and oxygen element spectrums having obvious changes in the whole experimental process can be found, and specifically, the high-reflection film sample has the appearance of two peaks in the silicon element and oxygen element spectrums, wherein one main peak and one shoulder peak are shifted to a low binding energy position.

As shown in fig. 2, the fitted map data can also show that the center position and symmetry of the main peak of oxygen element are kept unchanged in each measurement process, and the position and intensity of the shoulder peak are slightly changed with the increase of the charging times. High reflection film with such characteristics has poor loss performance, and the maximum loss reaches 100 ppm. Therefore, the method for accelerating the irradiation by the X-ray can effectively distinguish the loss performance difference of the film material. As the X-ray radiation can induce a large amount of charges on the surface of the high-reflection film, the charges are similar to those generated by the action of plasma, but the number is larger, and the purpose of the accelerated aging test is achieved.

During the analysis, we fit using the standard sherry model minus background and the gaussian-lorentzian profile. Compared with a Gaussian-Lorentz symmetrical peak shape function (namely, alpha and beta are 1.0), the LA peak shape function containing alpha and beta parameters can be well fitted to obtain an experimental result, and the fitting survival is remarkably reduced. Although the physical phenomena of spin splitting of an electron orbit, X photoelectron yield change, surface effect and the like influencing the XPS peak shape are not considered by adopting the peak shape function, the method is convenient for engineering application due to relatively few fitting parameters, and can effectively distinguish samples with increased loss and samples without significantly increased loss under the irradiation charging condition in experiments, so that the method is a convenient and rapid distinguishing method.

After statistics of the relationship between the changes of the peak shape symmetry parameters alpha and beta of the high-reflection film O1s and the corresponding loss changes are carried out (as shown in FIG. 3), the samples with better symmetry, namely the samples with alpha and beta between 1.0 and 1.1, have better loss stability and change less than 35ppm, while the samples with poor symmetry (the samples with alpha and beta deviating from 1.0) have poorer loss stability and change more than 35 ppm. By adopting the method, a plurality of batches of randomly selected high-reflection film samples are analyzed. In part of samples (i.e. samples with unstable loss), the O1s peak changes to different degrees before and after irradiation, and especially the characteristic peak of oxygen vacancy changes remarkably. After the experiment is finished, the loss of the samples is measured, and the loss is found to change by more than 100ppm before and after the X-ray irradiation charge treatment.

These experimental results demonstrate that X-ray irradiation can be used to evaluate high reflective film loss stability. The experimental method can effectively correlate the XPS analysis result with the high reflection film loss stability (as shown in figure 4, a sample with stable loss is in a dotted line frame), effectively solves the problem that correlation experimental data is lacked between various material analysis results and pm-level loss increase in early research, and can be used for links such as rapid optimization, process monitoring and the like of a film material process experiment.